Potluck salad party... I need help!

My 2nd best friend has been in school in Australia for the past 3 months and gets back 11/29. Another mutual friend of hers and I convinced her husband to have a welcome home potluck for our friend/his wife. She'll like it, but she'll also be tired and so, we 2 friends of hers will be basically hosting the thing at the guest-of-honor's house. There are a few glitches~ or maybe not that I need to figure out...

#1: She's a triathlete: salads are her favorite food, so that is the theme- potluck- but bring an item for salad. They have a dining room table which seats 6, should be enough room to lay the food out... then we all sit on the floor...

#2: Her husband just finished the floors. Hardwood, sort of parquet, very nice, over the whole space (maybe 20'x30'? Then there's an alcove about 10'~12') so there's a lot of space, but the guests I'm thinking of inviting have about 10 children under 10... who will be eating on the floor... unless I can bring my low table over... the family has a coffee table, too... Should I do some major moving of furniture around? Or is that unsettling- better to throw some sheets ont he floor and make the kids sit picnic style in the house? The husband said he wants it inside, the view, the possibility of inclement weather... There will also be at least 10 adults, probably more like 20... Not sure the husband is aware that I only know how to throw big parties... Well, he is, but he's not thinking about that--- and I don't want to overwhelm his wife, who will have gotten off a long flight (Australia to Hawaii) that morning...

#3) She's told me in the past she doesn't feel she has any real friends besides me, but she does! Everyone simply loves her and thinks the world of her- she's one of the nicest people, an inspiration, etc. I cohosted a party when she did her last Ironman triathlon for women for whom she was an inspiration... Cohosted with another woman whom she inspires tremendously (who also likes excuses to throw a party) we chose another mutual friend of ours who happens to be her neighbor for that location. She has since told me that she almost never sees that neighbor, and it was great to get together there... But since that party (2 years ago) they have probably seen each other only a handful of times. Weird to invite these neighbors who are nice, but busy, and live up a long driveway and are never seen, or not? That neighbor has a girl my boy's age, so we were in baby groups together, and her husband and I hit it off quite well; we all used to exercise together, but then our kids went to different schools and the mom in that household went back to school- and now she's a science teacher at my 13 year old's school. They are friends of mine, and friends of the person we're throwing the party for, and I would love to see them and they live 2 lots away from the guest of honor... Weird, or not to invite them? They have 2 daughter the same age as my friend's 2 daughters, but due to different religious beliefs + different needs for/from schools, their kids all go to different schools from each other and rarely have time to play, but do like each other...

#4: Same thing, different scenario for the woman who I cohosted the last party with... She hardly sees the guest of honor, hardly has time to see me except in passing or at get-togethers. I know she will want to come, and is a great party person, and always goes all-out and buys the best bubbly she can find, etc. And has a daughter the age of the older of the returning friend's daughter... but she, also goes to a different school; and while all the girls get along, they aren't best friends, and the moms all get along, but aren't best friends... Thinking now that maybe my friend hasn't had time to establish any real best friends besides me, and the woman who is cohosting this time (who moved over not too long ago- is my neighbor and my friend's surfing buddy- with a daughter the same age as the guest of honor's oldest daughter...) And a woman who lives about 30 miles away whose husband used to be my friend's husband's best friend, but they never have time to see each other any more...

So, I guess what I'm asking is should I invite these people who are social acquaintances/friends of mine who also are of the woman who is returning? When we threw the party post Ironman, my friend (the guest of honor) said that most of the women there she hardly saw... She was happy to have them all together, we all made sloppy-drunk (er, I mean tipsy) promises to stay better in touch, but didn't follow through for the most part... Of course, it is the start of the holiday season...

#5: Then back to the party situation: she has a tiny galley kitchen, then all this open space, hardly any counters, but a dining room table and a coffee table. How much cooking should we be doing in her kitchen? And what is the most efficient way to clean up so she won't be left with any sort of mess? We tried to talk the husband into doing a barbeque downstairs... The cohost's husband offered to bring his state-of-the-art bar-b-que grill over to cook on (he likes using it...) and I know my friend well enough to know she would prefer the mess be outside, that most messy kids eat outside... then we could move it all upstairs as night draws nigh, set up a table for nibbling off of, kwim? But that's not her husband's vision, and it's his house...

I'm thinking of telling him we'll make the party start earlier than 5, the time we agreed upon, and then we could cook outside, like maybe from 4? Have the bulk of the guests expected around 5- after work? Eat, with the party through at 8, since it's a school night... But I don't want to overstep my place, kwim?

#6: Oh, and finally, her favorite thing I make is my enchilada casserole, but it's made from whatever leftovers I have on hand. I'm somewhat embarrassed to make that for a party, but it's easy and uses up the stale corn chips that accumulate in the cubboard. So, should I make that, since she always swears she loves it, or make something somewhat more elegant? I'm leaning toward simply boiling soybeans, a good simple food, good for the vegetarians who are numbered among her friends, since I will be busy setting up the food table(s) and creating a beautiful build-your-own-salad centerpiece, and cleaning things up, keeping the party running smoothly... but enchilada casserole isn't a hard dish to make and people always assume it's fancier than it is, unless I start telling them how I needed to use up some chili, and had some beans left over, threw in some aging tomatoes and some chili powder and had these stale chips, + an old green pepper and... etc. but if I'm drinking, I wind up saying all sorts of inappropriate things (all the more reason not to bring enchilada casserole... not to mention the gas factor... )

So, any tips, any advice? Wwyd?