I agree with mousefan. If characters meet and greets are important, stop by the area in town square before making your way into the park. Once you're done here you can head into fantasyland, pick up fastpasses for Peter Pan and then do a few rides like Winnie the Pooh, Small World, Mickey's Philharmagic...and maybe even venture into the area with Dumbo, and the barnstormer roller coaster. In the early morning, you may be able to fit most, if not all of these rides in before your fastpass return time for Peter Pan. At that point, you'll be elligible for some more fastpasses and can head into Tomorrowland for passes for either Buzz Lightyear or Space Mountain. Again, as someone mentioned, the timing of the New Fantasyland opening could have a big impact on this.
We were at WDW last November, around the same time you'll be travelling. From what I remember the crowds were low, and I think you'll be surprised how much you can get done in the parks. I would get to the parks by, or as close to, opening as possible. This way you're not fighting the mid-day "crowds" (a relative term based on the time of year you go) to try to see everything.
Also....have a plan in place, but don't be so committed to it that you miss out on all the interests that the kids develop as they walk around and experience it all for the first time. I think many will agree that some of the best times at WDW come from those spontaneous moments when you do something that was never even a consideration. Have a great trip.