Hi,
Your family sounds like ours! I come from a family of 5 siblings and we are always getting together to do things. We love it! There are a total of 35. Two parents that started it all, five children and spouses, and 23 grandchildren spreading from 18 to 3 months. We get together on an average of two times a month just for birthday parties!!

Then we get together for all holidays and special annual functions and hiking and things to have fun together. We all wanted to give our kids what we had growing up which was big family functions and our cousins being some of our closest friends.

When we were there in 2005 with my parents we talked about doing this as a family function. We talked with one of the hotels and they were great about suggesting ideas. I like the idea that one said of just hanging out at the resort. I could see our family doing a lot of that!!

I could also see our family having a lot of fun at the water parks together! I'm not quite sure I could see us together doing all the rides together?!

Too many kids of differant ages!! I could see us breaking off into groups with differant ages of kids and cousins that wanted to ride on the same rides.

Doing the restaurant thing would be a definate thing and planning for the adults to go out together for one meal would be something we would look into planning. The older siblings would sacrifice one meal time to watch their siblings.
My biggest thing I would suggest is to try your hardest to stay onsite!!!!

That in my opinion would make the whole trip! If your anything like my family, unless it doesn't matter....it's always hurry up and wait for someone. It makes all the differance in the world to be onsite!! Fun is at your doorstep.

No driving to get there.

When your hanging out together at where ever you are staying, your still in disney with the disney magic!

You don't have to feel like you are waiting for someone to get going for the day. You are already there! My father said it didn't bother him at all in the mornings to wait for us to be ready to go to the park because he was already there and downstairs enjoying his coffee just enjoying himself while he waited. It's differant when you are waiting at an off site place and waiting for each other to get ready, you feel like the day hasn't started until you get to your destination for the day! It's easier to just go back to your room any time of the day!! Not so with an off site location. I think it would be easier to just hang after supper or the park closes when your are right there.
If you could possibly go in Sept for the possiblilty of
free dining that would save a bundle and be AWESOME!!

(the last two years during Sept. basically they have announced free dining for that time period - alot of people are hoping to hear of it coming out within the month. Also during that time there is Extra Magic hours for under 5 and their families-
http://disneyworld.disney.go.com/wdw/experience/experienceLanding?id=PreschoolersExperiencePage Especially for such a big group. You could be a grand gathering and do some "special" events that only grand gatherings can do!!

I am looking into the Safari Celebration dinner and the rest that they have exclusive for just grand gatherings. BUT, as one pointed out to utilize Disney as a grand gathering cooridinator and all the other perks, you have to be staying on Disney property. Check out this site and also ask Disney themselves.
http://allearsnet.com/pl/magath.htm
Well I had someother ideas, but I gotta get going. Good luck! Just keep hanging out here and asking questions and Disney is great for asking questions! BTW I would go through Disney versus
AAA as a
travel agent.
Also another bonus of staying on site is extra magic hours. Check it out.
http://allearsnet.com/tp/emhour.htm