Kids learn languages faster then adults

I agree that females learn languages better than males!
We only had to learn three foreign languages at school - but with nine, the gap between the genders would have been immense.

French must be easy for kids to learn, as I've noticed when I'm over there that even kids as young as two or three know how to speak it.

Five are family languages (complex family!), one religious language, and the rest are languages her mother or I have studied. We had a lot of long car trips and reciting phrases and counting in different languages helped pass the time, and it seemed like a game to her. I don't speak German fluently, but learned basic phrases and counting from my German grandfather when I was young. I ran out of German to teach her but then she enrolled in a short course in it at school. Some of the languages (Italian, French, Mandarin) were also reinforced in restaurants and travel. There have been a number of academics who promoted the idea of learning languages simultaneously; there was at least one language school that promoted a special course learning seven languages at once. I think when a child enjoys it, as she clearly did, it's best to give them all you can.

I do not think a special course in learning seven languages at once would be any good.
A language is not a lot of words you put together. It is a feeling for the words and certain behavior behind a language.
We learned three languages at school,but again it was just learning grammar and words and read and write. Getting into the heart of a language and really apriciate it there has to be much more. An interest in a country and in their stories and later on in their culture. and of course in its people.

I think it depends a lot upon the living and learning circumstances and opportunities of a child. When I traveled in Switzerland I was impressed that it was not at all uncommon for people to speak 4 to 6 languages. The most common ones there are German, French, Italian and English, which, given their geographical location, shouldn't be surprising. But when you grow up with 4 languages being legitimately spoken at home and in local commerce, those hardly count as a foreign language in school, so many Swiss will learn Spanish, Japanese or Mandarin as a foreign language. When you live in an environment with many languages spoken (Toronto, New York, Ivy league schools, etc.), NOT learning a language can mean walling off a large segment of the population and their culture. I've never felt it was merely memorizing and stringing words together; even at the age of 6 I realized that you're more likely to get what you want at a restaurant if you know how to ask for what it is you want. The woman pushing the dim sum cart readily understood even a badly pronounced Har Gow/虾饺, but not the English fumbling "roundish dumplings with the shrimp inside."

Get him a computer programming book, then he can learn the language of California estates with their own vineyards.

There are 4 languages in Switzerland.
Most Swiss speak one and some even two of these languages more or less well.
Very few can speak all four.
65% of the Swiss speak German
22% of the Swiss speak French
8% of the Swiss speak Italian
0.7% of the Swiss speak Rätoromanisch
Your idea that it is not uncommon for people to speak 4-6 languages seems not really realistic.
These informations fit very well with my experience when living in Switzerland.
For me speaking a language means be able to converse with people in their language and not just to order dumplings in a restaurant.

It's incorrect to say there are 4 languages in Switzerland. While there are 4 official languages, many others are commonly used. While Romansh is an official language, it has only 35,000 speakers out of an 8 million population. On the other hand, twice as many speak English despite it not being an official language, and even more speak Serbo-Croatian, Slovenian, Albanian and Spanish. The percentage of families speaking four or more languages corresponds (not coincidentally) with the number of households with college educations.

One counts the official languages in a country and not the dialect nor the languages spoken by foreigners. In hardly any family whatever Swiss or another European 4-6 languages are spoken by every family member. One can get along with a few frases and make oneself understood and can understand some but speaking 4-6 languages fluently is not common not even in academical educated families.

In Sweden about 150 languages are spoken, which just means there are people who speak one or two or these languages as their native language. It does not even prove they can speak Swedish.
And there are following national minority languages
Finnish, Same, Meänkieli, Jiddish and Romani chib

Official minority languages in Germany are Sorbian, Romani, Danish, North Frisian. And Low Saxon.
Recognised regional languages are additilly (= for official use only in some parts of Germany): Low Rhenish; Limburgish; Luxembourgish; Alemannic; Bavarian; Danish; Upper Sorbian, Lower Sorbian; North Frisian, Saterland Frisian; Romani; Low German.

I know a German young family who lived in Austria.
They did not like Austrian so when the child started Kindergarten they decided to move back to Germany so it would speak Hochdeutsch and they moved to Bavaria....

PS
I like dialects.

Nonsense. The US doesn't have ANY official languages at the national level, hence neither English or Spanish would count in your book. Official languages are mostly used for political reasons and decisions about translating and publishing government documents. The more important measure is the number of living languages in a country, indigenous languages, and contrarily, immigrant languages. English is not merely an immigrant language in Switzerland, it is an active living language. Knowledgeable sources place the number of living languages in Switzerland at 23, indigenous languages at 12 and immigrant languages at 11.
http://www.ethnologue.com/statistics/country

OK one counts the main language spoken in a country and not the dialect nor the languages spoken by foreigners.
And yes American English and Spanish would count in my book as they are the main languages spoken in USA.
English is an active living language in Switzerland - yes but not within the families. nor on radio or TV. Films are sent with undertitles.
English is almost second language in Sweden, but of course we Swedes speak Swedish with oneanother. English is used at universities and many different firms.
Countries were English is best spoken is Denmark, Neatherlands and Sweden.
I told you about languages in Sweden and you come back and tell me it is nonsense as in USA it is different.
When you learn about another language and a country don´t tell that native person what they said is nonsense.That person probably knows a bit more about his/her country than you do.

Georges Lüdi; Iwar Werlen: "Sprachenlandschaft in der Schweiz", Neuchâtel, co-published by the Bundesamt für Statistik is a very interesting source.

According to latest statistical data from the above mention Federal Statistical Office, the most widely represented languages in Switzerland are, in order of frequency: German, French, Italian, Bosnian-Croatian-Serbian, Albanian, Portuguese, Spanish, English, Turkish and Tamil.

This was a really great gift you gave your son, and he is at a really great age to learn another language. Before puberty, children can learn how to speak another language with the native accent. This is something that is difficult to do for adults, and even impossible at times. But if your son really wants to become fluent, he has a long way to go from Rosetta Stone to being an active speaker. It may seem as if children learn languages faster because they generally only have to say the simple things. However, adults can actually out-perform children because of the high level of language they have to master.

Keep his language studies going and he will be on a great track to understanding French on an academic level.