I think the most important you need to be sure to include is a category for "Other;" the only thing you can be sure of is that once you get to WDW, there'll be something you want/need to buy that you didn't forsee. If you're running your budget via little enveloppes with specific things written on them, now you've got to figure out which to take from to pay for the unforseen item, how to cover the other thing, etc.
You're on vacation; why create this problem for yourself?
What I do is pay for everything that I can ahead of time; airfare, car rental, hotel, park tix, etc. That leaves just the food and "other" once we're there. I put as much as I can on a credit card, keeping a rough running total in my head each day, vs. what I estimated ahead of time. Sometimes it ends up being less, sometimes more. If everybody's in a good mood, the weather is nice, we're all "in the zone", I'd be very reluctant to say "sorry, we have to leave the park and eat at McDonalds because we don't have enough money left in today's 'food' enveloppe to stay in the park and eat here."
Again, you're on vacation! Better to skip a few dinners out once you get home, if you find that you went over your budget with food at WDW.
As to "other," you don't know what it will be, but you know that it'll be there. If it rains, you may need ponchos. But, if it doesn't rain, you won't. You may decide to rent the little motorboats. Or, you may decide not to. You may decide to go to DisneyQuest. Or, you may decide not to. You may decide to take a day off from Disney (perish the thought! Sorry, Mickey!) and do one of the other things available in the Orlando area.
Point is, you don't know how you'll feel, and what of these "other" things you'll want to do until you're actually there. So, why stress over trying to lock in a plan/budget ahead of time?
Anyway, that's the way we do it.
What also helps is that I'm inherently cheap; I have an allergic reaction to wasting money, so that helps keep the "other" from getting out of control!
Have fun,
Dave