In addition to all of the above, you can use rider swap to let the 5-yr-old ride Big Thunder, Mine Train, and Splash Mountain (and Space Mountain, if they're at least 44 inches tall).
The reverse question is, what to skip?? With only one day, at those ages, I would skip Stitch (2 yr old cannot/should not do, and not worth the time to swap), most meet n greets (maybe just do 1-2, because they can take awhile and you can't predict the kids' reactions), Pirates of the Caribbean (it's an iconic ride, but our almost 2-year-old found it too dark, and it can take awhile), Peter Pan, sadly, if you don't have a fastpass (also iconic, but the line takes forever, and you only have 1 day), the treehouse and tom sawyer island (both take a fair amount of time and energy), Country Bear Jamboree, and Hall of Presidents. I would try to fit in everything else.