Agree, you want to go early for a few hours, leave in the afternoon when it's hot and crowded, then come back at night for a few more hours. The parking lot opens at 08:30am.
You"ll be pushing a stroller most of the day. The kid will enjoy the playground behind Shamu stadium, bring a change of cloths because they can get wet.
If you are going to eat in the park, do it at 11:30am before everyone else realizes it's lunch time. Arrive to each show about 20 minutes early, especially Clyde and Seamore.