1. Take it slow.
2. Plans lots of breaks.
3. Use disposables (sippy cups, bibs, spoons, changing pads)
4. Use the A- and B-ticket rides for breaks (riverboat, train, hall of presidents)
5. Make time to let them walk around at a play areas (staying all day in a stroller is going to be tough on them
6. SUNSCREEN! SUNSCREEN! SUNSCREEN!
7. hats
8. pack or ship a case of water to your hotel to carry in your park bag
9. refill diapers and wipes at mid-day breaks
Rides:
MK - train, riverboat, county bear jamboree, pirates, jungle cruise, small world, dumbo, winnie the pooh, philharmagic, peter pan
EP - not as much to do here, but exploring world showcase, Nemo ride
DHS - no recommendations
AK - dinoland, camp minnie-mickey, safari (but they'll have to sit in the middle), train, affection section
Where are you staying? Did I miss it? Most of the hotels have kiddie/wading pools. I know Pop! has a fountain to play in.
Have fun!