Are you staying on Disney property? That certainly makes transportation easy.
Do you have a mix of little kids, older kids, and adults? If so, the adults can trade off so that everyone can get a date alone with their spouse. Be open to non-dinner options like a nice lunch etc.
Are you doing any of your own food - we set up a buffet line with bagels, peanut butter, cream cheese, juice, fruit etc. We brought cereal and just bought milk from the food court. It was pretty easy and saved a lot of money over the course of a week.
It is usually not practical to expect to do every ride or attraction together but it can be fun to meet for certain things: IllumiNations, Fantasmic, each of the parks has a 3-D movie, etc. If everyone is tall enough, Soarin' at Epcot is gentle enough but fun enough for a cross-section of ages. A fun "togetherness" shot is if you all can fit in a log at Splash Mountain - they'll allow 3 to a row, if you fit. We had twelve in a log. It was tight but the photo was absolutely worth it.
The water parks seem to lend themselves to visiting. They'll allow you to bring in a picnic (no glass containers though) - so everyone finds their way back to the meeting point to eat. The family slide at Blizzard Beach is fun too.
If you have a families with younger kids, the campfire sing-along w/ Chip & Dale (free) is a lot of fun. We ate at the Trails End restaurant before the sing along and then stayed for the movie (free) that they show outdoors on a large screen afterwards.
http://www.buildabettermousetrip.com/activity-campfire.html
Our family did a special dinner at Boma at the Animal Kingdom lodge after our Animal Kingdom day - that went very nicely.
The group thing you might be thinking about is the Magical Gatherings program. Here are a couple of links with information:
www.disneyworld.com/magicalgatherings
http://allearsnet.com/pl/magath.htm