I know I'm late to the thread, but I'll still add my advice: take both cameras. However, set aside one day, or some speciic times, as your "big camera" time.
The thing with Disney and kids is you do t want to spend the day lugging gear around. Furthermore, you want to be able to enjoy the time with the family instead of being the dad that spends every waking minute taking pictures.
My wife and I go yearly and have found the p&s works freat for quick, candid shots and overall just makes the experience easier and therefore better.
We do have times where we'll go out to the parks with the dslr with the sole purpose of getting great shots of scenery, family, etc. Those times are set aside as photograph time.
Of course, using the park hopper option makes this more feasible as we spend a few hours hopping to different parks and hotels to take pictures. One fine example of best use of dslr is the nighttime shows (fireworks, parades, fantasmic). A regular p&s just likely won't yield satisfying results in these scenarios so the dslr is a must ... At least for us.
We've set aside a whole day strictly for touring the parks and taking it all in, rather than riding rides. This allows us the freedom to stop and snap nice shots rather than feel rushed and tied down. We also sometimes come back to our on property resort and grab late lunch/early supper, and go back to the park with the dslr.
So, again, my recommendation is to take both down to Orlando, but only use the dslr during set aside hours and let the p&s serve you during the majority of the trip.
