I don't usually have a daily limit. We almost always get the QS dining plan, and during a 7 to 10 day trip, one or two TS meals OOP. I usually have $75 for each of my grandmunchkins, in their own envelopes that Mommy holds, and bring an amount for the three or four Christmas ornaments I buy as a gift for each of them. I ship them home, which is an extra cost also.
I then think about any events we have planned. Out of pocket meals, tips, for magic express and bus drivers, concierge desk tips, TS meals, Mousekeepers, etc. I then come up with what I want to spend.
So I have more of a total trip budget. I usually have money left, when all is said and done.