The very best suggestion I can offer (especially with 3 very young children) is to plan to be flexible. Go with the flow and be sensitive to what the group might need at any moment (and it may be to take a nap or eat ----- and keep everybody well hydrated!).
Make a general schedule and decide if you're going to try to go to the early entry park that morning, or the family needs to sleep in. Read about the parks so you understand what's available and identify your "must do's", "would like to do", and "will do if time left over". Pay attention to how tired/irritable the kids AND the grown ups are getting.
In the hot weather, it's really better to try to get to the park as early as reasonably possible and then head back to the room or DD for lunch and the pool. A nap or rest time is strongly encouraged, unless your kids are super energetic in the heat. You can go back to the parks in the later afternoon or early eve, when it's a little bit cooler. Kids can often stay up later if they have a nap or rest period. DO NOT push when it's hot and people are cranky.
After a few days and a visit to each park, you'll start to identify what you like best and feel better informed about what to do next. Stormalong Bay is sensational, so do plan to take advantage of it. Between that and visits to DD or a character meal, you can easily plan for several resort days when you can sleep in or do a water park in the AM (less crowded then).
Hope you have a great trip!