Where are you staying and how many park days will you have, will you have single park tickets or park hoppers? It all makes a difference.
Another vote for Epcot but I'm biased as it is always my arrival day park. I usually get there somewhere between 1 and 3 (I drive down from Georgia). I'm usually hungry and Epcot is usually having a festival so I snack around WS making my way to the front of the park. Sometimes I'll ride a few rides along the way then I'll hop over to whatever park I have a reservation for the next day. That allows me to knock out a few rides since most parks are less busy at night. You will need to check the park hours for your arrival day, depending on the time of year, they close earlier.
By the way, I'm 65 (will be 66 my next trip in April) and usually go for at least a 4 day trip, most of the time 5 day, my trip in April will be 6 1/2 park days. I always have hoppers, never buy
Genie+ or ILLs. Since I'm older, go often and can't ride some of the more intense rides, I have no problems riding every thing I want to ride by hopping. I always stay on site, usually do a split stay with a value the first few nights then switch over to Swan/Dolphin for the rest of the trip.