I always try to stick to my kid's "at home" schedule as much as possible. So, we typically do rope drop (my kids are up at the crack of dawn) and afternoon break/nap, but leave the parks well before the fireworks.
Familiarize yourself with the Rider Swap program. This allowed my oldest to ride things twice with minimal wait a bunch.
Packing....puddle jumper for the pool, if your kids aren't strong swimmers. My kids care more about the pool than they care about the parks most of the time.
The stroller is a good idea. I'd bring some snacks into the parks, because even if they eat anything, they might not eat anything when you want them to eat. Just being able to hand them their favorite snack, while waiting in line can be helpful. This is also helpful in the mornings when all the other adults are asleep but the kids are up.....and hungry.....with energy.
Buying fans in advance can be helpful. The cheap
walmart ones are a lot easier to tuck places, than the big spray kind they have at the parks. There are also fans that you can get that attach to the stroller. It doesn't tend to get super hot in December, but it gets hot enough.
Don't be afraid to split up, or at least tour in zones. My daughter hardly wanted to ride anything on our last trip, when she was 4. She just wanted to play. My oldest went off with an adult to ride to his heart's content. If you're going to have extra adults, then make use of them. There was lots of stuff my middle son wasn't big enough for too, so we did Rider Swap for select attractions, but most of the time we just split up and rode the calmer stuff with the younger two.
Plan on lots of bathroom breaks, especially if you have a recently potty trained child (and by recent I mean within the last year). In fact, if your almost 3 year old isn't potty trained yet, I probably wouldn't push for it before your trip. IMO, it's a lot easier to change a diaper than it is to deal with an accident. I'd also plan to bring a change of shorts for any child. I'd bring extra underwear, in general, and don't hesitate to just toss any that contain an accident, like you would a diaper. With frequent toilet breaks, when "everyone goes to the bathroom now," you probably won't have accidents, but even my 11 year old struggled at
Disneyland last week. He's older, so I can only argue with him that he needs to at least try so much. It's just too easy to get distracted, and the bathrooms aren't always located conveniently. I'd also test your kids in bathrooms with automatic flushers in advance. My daughter was/is terrified of them, so a carefully placed post it note or my hand helped us get through bathroom trips at Disney.
I always bring extra plastic bags with me, especially if I'm not doing a grocery pick up. That way I can have a way to tie up anything that might get wet.
Just last week, my son didn't hang his swimsuit in the bathtub properly on our last night, so I ended up putting it in a plastic grocery sack for the flight home.
Overall, have a solid plan, but be flexible. Sometimes everyone just needs to sit on the curb with an ice cream.
