If you are on Facebook I'd recommend you join It's Orlando Time.
DH and I usually budget $350 per day and as the holiday goes on, that amount will increase as we won't always spend that much. Some days we spend a lot - all meals out and all the souvenirs we like, plus parking, but it rarely comes to that.
We like to bring our own packed lunch and buy at Walmart as we find we just can't eat junk or pasta all day every day. Kiddies might prefer this too! At the parks, you can ask for iced water at any restaurant or in kiosks and this is free. This is not advertised of course as bottled water is at least $3 per bottle and available everywhere. That saved us tons last time we went.
We liked to plan a little. For example, we knew a couple of days in advance which parks we would visit on a given day and tried to book the three fast passes close together early in the morning so that we could use whatever, whenever after that. However, we did stay in a villa with our own pool and it was lovely just to have chilled pool days as well. Some evenings we would just order a dominos pizza and that would feed 4 adults and a child for $9.99, plus tip.
As a previous poster said, if you can, fly indirect. Saves so much money. Pre covid (so don't know if this is still the case!) I found that United Airlines were the only company that included baggage in their prices. It would say at the time of booking that it didn't, then on the booking confirmation it was included 🤷♀️. Just something to keep in mind. We went to the USA twice in 2019 and flew with United both times and this was the case on both occasion. Flown with United a number of times before that too.
I've never booked through the airline directly either, I search sky scanner for months and on occasion, we've booked weeks (and even once the day before) we wanted to go to get the best price on flights. Of course this isn't practical to book just before with children to factor in, but never go directly to the airline first!
You will have a fantastic time! I miss Florida sooo much and the moment we can book flights out there, me, DH and our DD will be off.