Can everything be done in 4 days? Everything with MaxPass can be done in 2 days, 3 days if you're taking your time.
You need 3 days at least unless you're powering through everything. 4 days should be fine in my opinion and it allows you to re-ride all your favorites. I've thought about buying a 4 or 5 day in the future since the extra days are so cheap and use 1 or 2 of them just for Fireworks/parades at night and a few rides.