IN my experience (5 trips with at least one child under age 3 on each trip) you don't need to skip any park with kids those ages, if the adults are interested in and want to see all 4 parks. Kids can have a great time in any of them! Now, if you WANT to skip any, then sure, you can load up on extra MK days and eliminate any of the other parks depending on your family's interests. In that case, I find Hollywood studios easiest to skip - my favorite attractions there are not for little ones (rockin roller coaster and tower of terror) and the park is "show heavy", meaning lots of time sitting and watching plus a bit more effort to plan out timing, both of which may be harder for families with young ones.
Fastpasses for little guys in MK - I agree with the above and could add 7dwarfs mine train in 4year old is tall enough, Big Thunder Mountain RR or Splash Mountain if 4 y.o. is tall enough and a little daring. Enchanted Tales With Belle can get long waits and is great for those ages.
At AK, definitely fastpass the safari.
DHS - I'd do Fantasmic if you'll be out for the night show, and perhaps Frozen Singalong or any of the other shows (except Disney Jr, where the fastpass seating is actually a bad view and standby is better)
Epcot - Living with the Land and the other choices depend on whether mom and dad will utilize child swap and ride things, or whether you're only doing whole-family rides.
ETA: I love your dining choices for those ages! You'll meet lots of characters and unless you have favorite characters that aren't included in those meals, you won't have to spend time in character lines in the parks!