Ok, I know this may sound bad, but it's really not:
Watch every penny, EVERYWHERE!!
Groceries: Go cheaper than the norm at least HALF the time, more if you and yours can deal with it.
I have read folks feel sorry for those who bring in their sandwiches, wrapped in foil, to the parks. Ok, me I will still bring in a sandwich the first and/or second day...but if it really bothers you of what others may think do this...do it at home for a few menus every couple of weeks, until (and after if needed) your trip. I honestly will do both, do I want folks to feel sorry for me, heck no. As a single Mom with NO help from Dad, knowing I feed, clothed and keep a roof over my kids head is a GREAT feeling!! I even help put one through college....
Do you do outings? Cut those down to a bare min. Remind your kids for that amount of money they are that closer to a trip to WDW. We rent Disney movies only once every two weeks. Olders ones are much cheaper. Got a few at a cost of $2.12 each (yeah Blockbuster).
Make your own T-Shirts with iron ons or look for great sales, on clothes, to wear in the parks. You can make them as a surprise as a birthday gift, an Easter basket extra or just a gift before going or better yet, after you arrive....
We use to try to eat at BK, Mickey D's or order pizza once a week, not now. I love to grill anyway, we just now do it twice a week instead of one for the burgers. Pizza-make one at home...a cheap make at home kit under $3.00, add a little extra cheese $2.00 or less extra. Beats $11.00 or more from delivery service.
Do you run around much daily? Can you cut this down to once or twice a week and save on gas?
Look for other posts here, where your kids can sign up for possible surveys and earn CASH (well a check but for cash)!!
Back to the outings part of this post....got a tent...do a camp out in your back yard if posible to give the kids of an "outing". You can mix the cook out with this, etc.