My family joined three other families for the 2002-2003 New Year's week. We arrived on the Saturday before, the other families arrived on Sunday. Three or four months prior to the trip, my wife (the Disney nut) put together an "itinerary" for the trip: Arrival Sunday we do this, Monday that, Tuesday something else. Each day was a different park, with New Year's Eve being a park-free day (for crowd reasons; also I played golf with my buddy that day). DW included dinner plans (cheap, moderate, expensive) for each evening and we all got into a private chat room to discuss and finalize the plans. We all agreed that the park of the day would be the group's destination, but that touring each park would be at each family's own pace. We would re-group at dinnertime and then go do an evening activity together (Illuminations, Spectro, etc.).
In execution of our plan, we found that everyone's desires were met, everyone had a great time, there was room down-time (always important) for the youngest of the group (and the oldest, too) and no outgrageous amounts of money for meals was spent.
The only thing to watch out for is that many restaurants cannot accomodate extremely large parties: DW wound up making priority seatings for two groups of 8, after reading here on the board that if you show up early enough before your PS, the restaurant staff can sometimes put the two groups at one big table. The only time it didn't work was at Crystal Palace, we were at two tables, near enough to each other.
What ever you do, don't expect perfection. There are still limits to what the Disney Cast Members can do and if you work within these limits, you will experience Magic beyond belief.
My final advice: Research, Research, Research! Then choose one person to put together touring plans for later discussion and finalization. Get input (Grandma wants to ride Pooh, Uncle Ted loves Space Mountain), and plan around these requests. You will also experience Magic, even doing the research!
