correct

The first sentence is correct. The second sentence is incorrect; however, it is an idiomatic way of saying that which many native speakers would use.

Absolutely.

And austere, the way to be sure is to drop the "my son and".
Imagine the sentence with a singular subject: "I have a team approach".
"Me have a team approach" is obviously wrong.
So, "My son and I have a team approach" is the correct one.

The same technique works for objects:

examples. "He gave it to me. He gave it to my son and me."
From this you can see that "He gave it to my son and I" would be wrong.

Totally agree.