Your biggest problem is going to be EPCOT with just 1 day there. EPCOT was by far DD's favorite park other than MK at both those ages. With the tiers, you have Frozen, Soarin and Test Track and you can only pick one of those and your kids are not old enough to do the single rider line. At age 4, DD loved Soarin and tolerated Test Track. At age 6, she liked both. Assuming your kids are not yet totally burnt out on Frozen, I guess you will have to try to get the FP+ for that one-- although it is going to be a VERY hard to get FP+, I am expecting. I would do that if you can and then try to get there really early to get to Soarin at the front of the rope drop crowd--- with it being a whole new movie which almost makes it a new ride- those lines will be very long this summer. My only concern with that for you is making it the 4 year old's first ride. If it scares her- it might be hard to get her on something else. We told DD she would be flying like Peter Pan, her first time (she was 3)-- after the ride she corrected us to tell us we were wrong and we were in a hang glider like Diego. TT probably will have the shortest (but still long line), so I would just try to get to that one when the line isn't horrible if at all possible. When Frozen was not in the mix, several times we have loaded our FP+ in the morning to try to get another tier 1 (either Soarin or TT whichever we did not have for the day- or we would even had taken Illuminations), but we have never even once been able to pick up another Tier 1, even when we have moved up FP+s between rides to try to get them done as fast as possible after park opening.
Other FP+s for Epcot. Since FP+, we have actually found that the attractions we usually rode walk on often have 1/2 hour rides. I would say the ones we have used the FPs to avoid longer lines have mostly been Nemo and Imagination. Turtle Talk with Crush isn't a bad idea- but we have gotten into that pretty easily without a FP+. DD also loved Living with the Land at those ages, but even since FP+ we have typically been able to do that ride with a line of 20 minutes or less. Spaceship Earth, even since FP+, as long as we don't go first thing in the morning (people enter the park and stop there since it is the first ride they pass) we have still always walked on- or waited less than 10 minutes for- it.
MK--- The priorities for us would be 7DMT and Peter Pan. The worst thing about FP+, was usually DD rode Peter Pan several times a day-- there were days when we just FP that one several times and never pulled a different FP. Even if you hit PP within the first 5 or 10 minutes of rope drop before the line builds (and it will have built by about 15 or 20 minutes after rope drop), your 4 year old may be begging for another ride on that one. The rest really depends on your kids. DD hated BTMRR at those ages and still does today. Do you think you think your kids will be thrill seekers and wiling to ride Space Mountain? If so, I would do that one of your days. Splash is a really good one to have in hot August-- especially in the hot afternoons because that is when the lines get the longest.
AK-- Safari. As far as the rest, when DD wouldn't ride EE, DH and I would still use FP+ on it and take turns riding-- or you can still use the single rider line. DD was tall and was tall enough for that one at age 6, but was not going to set foot on it. Other than that, Kali - again in the afternoon for hot August is a good choice. You can also FP+ the Lion King or Nemo. The FP+ line gets to enter first which gives more of a seating choice. Also, it guarantees you entry at the time of your choice-- we have been lucky with Lion King doing standby and have never been turned away, but people do get turned away.
DHS--- This is another place you are dealing with tiers. With kids that age, I would say TSM. They have opened the other track recently, and I have heard that has shortened the line, but I don't know how short they will be in the Summer Months. Plus, even if you hit it with a short line, it can't hurt to have a FP+ to get them a 2nd ride. This unfortunately leaves the parents out of RNRC- but I'm guessing neither kid is tall enough to ride that one. RNRC does have a single rider line- but it often is very long itself. Another good FP+ for that age is Star Tours. That line is typically not too bad unless you get there right as the Indiana Jones show gets out, but it doesn't hurt to be holding one just in case. That ride can have different scenes, so you might get a totally different ride as second time. I don't know if your girls have gotten caught up in the Star Wars frenzy, but mine definitely has and she loved the ride even before she had seen any of the Star Wars movies.
