I gotta say, I admire your commitment. With everything you've been thru, its amazing you can continue to search for the good.
I don't have a lot of advice on big family planning, but I did read some tips on here somewhere recently, and I remember one thing that seemed like it might apply to your situation.
That person was also going w/ family that they weren't sure would really benefit the group's experience. They made separate plans, but left open "group" days. I.e. - If they were going for a week Mon-Sun. Everyone booked their own hotels for those dates (allowed everyone to do their own price range, bargain hunting etc.) Then, the original planner - who happened to be the DIS-er and the only one who wanted to plan early b/c she knew the benefit of ADRs, etc, planned out her reservations. She updated everyone else and said, we have plans to be at, for example, MK on Monday with an ADR at Crystal Palace at noon. If anyone would like to join us there after 1pm for the rest of the day, lets set up a meeting spot. Monday night, we will be watching Wishes if anyone wants to join. Tuesday is an open day. Does anyone have a park they would like to go to? Etc, etc etc.
Hope this helps.
Gotta go. Lunch is done. Take care TK'ers.