We went two years ago with kids 3 and 5 at the time. First of all, if you think you can do “everything” in 4 days then you will be astonished when you arrive. We were there 7 full days and fell far short. However, we did not just do Disney. We went to Magic Kingdom twice, EPCOT, Animal Kingdom, SeaWorld, Universal, and Adventure Island.
I’d agree with pilot more or less.
We spent 6 nights and 7 days. We stayed at the Disney Hilton (not owned by Disney but considered a Disney hotel, with discounts, early admission, free shutttle bus, etc.) and had a Junior Suite, which is really just a big room, with two double beds and a convertible sofa for $1546.
We spent $1058 on park tickets, stroller rental, and parking for the non-Disney parks that we had to drive to. The park tickets for Disney are discounted when you buy for several days, although there is no such thing as a hidden bargain on Disney tickets. (You don’t say how old your kids are but I highly recommend strollers even for older kids. There can be an enormous amount of walking and kids will tire of that quickly. A double stroller rented at the parks worked out great for my kids.)
We rented a car for $330 for the week.
We spent $937 on meals and did not go to any adults-only type restaurants. We had an excellent experience having lunch at “The Sea” at EPCOT. My wife and I had a meal suitable for a good upscale restaurant while the kids sat next to us eating PB&J and drawing with crayons. The only restaurant I’ve ever been in that caters to adults and children at the same time. Also one wall of the restaurant is an aquarium. I highly recommend it, make reservations ahead.
I also recommend the character breakfasts at various venues around Disney. Make reservations.
We spent a whopping $200 on T-shirts, caps, photos, pins, and other souvenir type stuff.
About another $750 on air fare from DC.
After a few other odds & ends, total damage: $4900.
We didn’t go all out, but neither were we trying to save money. There are lots of cheaper options if you want to save and I’ll bet you could spend 60% of what we did if you stay off site and go easy on meals. One hotel that looked good to me was a local Holiday Inn that has rooms specifically designed for families with young children. Check Expedia.