Definitely book a package holiday so your transfers are included to reduce the stress.
Try to get reasonable flight times so you aren't getting up too early, arriving too late, and also from the return side that you can just check out and get on the transfer bus with a small piece of hand luggage with essentials, rather than hanging round until the evening (some companies even offer a hotel room to change in, so you can swim or stay around the pool for a bit and change clothes if you need to check out of the room before your transfer.)
Kids activities are always a plus. Definitely look for kid friendly pools at a resort. Much easier to manage two in a small splash pool area, and a little playground on a cool evening helps.
I don't really do AI now as my DC is grown up and we are out and about all day, but for young children it's a brilliant option. There's always something they can find to eat, many will have pool snacks, ice cream, afternoon pizza etc so you won't stress if they miss a main meal time because they want to sleep in, stay in the pool, take a nap etc or you don't feel like managing them round a buffet system.
You also don't have to keep your purse on you and don't need to pay out for full portions of spaghetti that they just fall asleep over. I learned that through experience. 😅
I used to also pack a bottle of squash and some snack bars just in case, and also to keep up hydration if it was getting hot.
Don't sweat the small stuff, if they live on cucumber slices, or chips and ice cream for the week, just go with it.