I would add a 5th day on to the hopper and go for it. We love going to a park on arrival day - we consider it a bonus day. Although, I am not a FP+ fan at all, that is the one time it actually comes in handy because we can book FP in advance for that evening. We currently prefer EPCOT or DHS for arrival evening- whichever has later hours- because of the tiering in those parks. It helps to get in another of those tiered rides. I don't know if Soarin is back open yet when you go, but it sure is nice to have that "bonus" day to get a FP+ for either Soarin or TT, when you are limited to one of them on your other EPCOT days. So, I think your EPCOT idea is a good one. The only thing about making an ADR for that night, is that you have to be willing to pay the $10 per person for a no show if you have flight delays/flight issues. I think your estimate of 4:00 p.m. is about right- we usually find ourselves in a park about 3 hours after the plane lands.