Planning a trip with a group can be tough. There are so many things to consider - people's tastes, what people want to do and see, where to stay, where to eat. It's exponentially easier when you have a group of friends like mine - we're all pretty flexible, and we're not against the idea of "subgroups" going and doing their own thing for a while. We're low key people, and I have a feeling it's going to make planning our trip to Italy next year for our friends' wedding a fun process rather than a tedious one.
The one thing to keep in mind is the constant changing of plans - take, for example, the itinerary. Granted, the itinerary I posted for the trip was SUPER rough, but it's only three days later and things are already changing. When I did that itinerary, I was thinking that the majority of people would want to do their own thing after being in Florence. I knew one friend wanted to visit the people she worked for in the Alps, and thought it might be fun to detour there. But I forgot that about half the people going have never been to Italy, and that for them, Venice might be more important than the Alps. So I took the two days assigned to the Alps, and put them in Florence and in Venice instead. That way, my one friend can still go visit her people, but others have more opportunity to explore the areas they're interested in. I also made a split on one day - some people want to stay in Rome a day longer while some want to go up to Siena with the bride and groom.