Being in a group, I don't know what kind of leeway you'll have to do what you want, but I'd look for a good "comparison of WDW to DL" guide and figure out what you want to do. While some (OK, a lot) of personal preference is involved, most people will agree that some rides are better at DL (Pirates of the Caribbean, probably Space Mountain), some are better at WDW (Splash Mountain, Snow White), and some exist at DL but not at WDW (Indy (unless you count the Dinosaur ride as its equivalent), California Screamin', Monsters Inc., Sleeping Beauty walkthrough). There are a lot where they're kind of a toss-up as to which is better, too, or some where it's basically the same (Soarin', Star Tours, all 3-D movies except the upcoming Captain EO

).
My priority would probably be to aim for rides/attractions that are better (or possibly just different) at DL and rides that WDW doesn't have, and plan from there. Once you've figured out what you hope to accomplish (and keep it reasonable) you can devise a general plan of attack. If you keep your "must-do" list fairly short then you will probably avoid being disappointed better than if you planned to ride and do EVERYTHING, because the latter just isn't possible.
You should be able to have a great time--on my first (and so far only) trip to WDW, we did almost all of Epcot and much of DHS in one day and I had a great time, even though as a WDW vet you'd probably say (rightly) that they can't both really be experienced in one day.
