We try to get in as many rides as possible in the early morning (when the crowds are thinner and the sun is lower), then enjoy a nice, air-conditioned break around lunchtime. If you prefer the breakfast buffet, you can make an ADR for last seating. Especially on a day when the MK opens early, you may be ready for a break in the late morning.
It just depends on how you want to tour the parks, really.