You will be glad for the mid day breaks- I think these are more crucial than a full day break. Plan on leaving after lunch for at least four hours. You may consider more than one early evening back at the resort. Unless your family just loves the shows, three days in HS seems like a lot. There isn't much to do for the four year old unless they are tall enough for ToT or RnRC. If you get your boarding group one of the first two days there, and can decide between the three tier ones ore r ope drop one, 2 days should be enough. Keep watching a lines app, but so far MMRR seems to have reasonable wait times later in the day if you don't get a FP. If you rope drop, I'd rope drop Slinky Dog. I also would take car for after evening show nights if you need to take a bus. Someone else can weigh in on the skyliner after fireworks at HS and Epcot-not sure how quickly they get you out of the parks after those.