Definitely use the free hours you get with the hotel and look for the tips on what bits of the park open when so you can go straight to some of the ‘big rides’ first and get them done.
There are two ‘alleys’ either side of Main Street as you walk in that are much much quieter so aim to use them depending on where you’re going.
We bought sandwich bags and a cool bag and made some rolls up from the breakfast buffet, took some fruit/yoghurt for snack during the day and then just had dinner later on.
If your 4yr old has Disney costumes/teddies then worth bringing them of you can fit them in. If they are holding a certain toy/wearing a costume the ‘real’ Donald/Goofy etc will make a point of waving at them or coming to see them during the parade. (My two learnt the order of the parade and would fling Peter Pan over their shoulder and grab Donald, then drop him and wave Pinocchio around!)
Comfortable shoes and bring the buggy - good for carrying lunch, teddies, coats etc anyway and there are buggy parks at every ride.
After the first day the parade would be a good time for you to split up and maybe take your oldest on some bigger rides while the other takes the little one to watch the parade again. (Oldest should definitely watch it at least once though)
Fireworks are cool but I wouldn’t worry too much about getting a great spot for them, they’re in the sky after all. We watched them from just by the main gate so we could shoot off back to the hotel first afterwards.
If you’re anything like us then a couple of bottles of red wine for you two to share once the kids are asleep go down well. Ours were too knackered to stay up too late (and we were as well!) but it was nice to have half an hour to take the edge off before going to sleep…
I think that’s everything, have a lovely time! It’s so great watching the kids watching the magic!