This will be my first trip, but I've gotten tons of tips from this board (mostly from back when the search function was WORKING!!!!), so I will share what I can think of.
- definitely bring snacks - granola bars, fruit snacks, crackers, etc.... I think the only thing they object to is a cooler with complete picnic lunch - snacks, juices, water, etc should be fine.
Know the location of the baby care centers in each park - good place to unwind with young ones - there are apparently microwaves, high chairs, comfy chairs for a rest and a snuggle, etc...
Agree with pp on the dark rides - I've been warned about Snow White, Toad, Pinnochio, and I think that's it....also, the show It's Tough to be a Bug is apparently supposed to be rather intense for some youngsters (we're steering clear, personally) Our basic rule of thumb is going to be - if in doubt, don't ride!
Bring a change of clothes/shoes for the little one (and maybe you too!

), since there are various water play areas where a kid can get fairly soaked, and spring can still be cool in wet clothes.
Save time by applying sunscreen when in line to get into park (if you are up and at it that early) Keeps young one occupied while waiting.
Bring along various treats/toys for bribing while waiting in lines. Bubbles also have been recommended for keeping little ones entertained in long waits.
That's all I can think of for now - will post anything else if I think of it.
My kids will be 5, 3 and 1.5 for our trip in May, so I've done a bit of research on this subject!
Carm