Well, there's a few places to start...
First, when are you going? Where are you staying? How long will you be there?
Secondly, are you on the dining plan? If not, are you interested in nice sit down meals?
From there you can figure out what park you want to go to depending upon EMH's, restaurants/ADRs you might want to try and also parades/fireworks you want to see. Also consider asking everyone in your group for their top 5 list of things they'd like to see or do.
That should help get a good foundation, but I'd really shy away from too strict of an itinerary. Vacations are supposed to be fun and relaxing. Too many things can go wrong with too rigid of a schedule. Enjoy your time!
Hope that helps! :wave: