Last year, the 5 of us (3 adults and 2 teens, 10 & 13) budgetted $150 per day. We had some spare money for parking and fuel (around $ 350 I think). We actually had money left over. We were there for 3 weeks. The girls each had their own $ 25 a day budget.
However, we do not go for the expensive meals, nor do we drink alcohol except for the occasional cocktail.
We go out to breakfast (buffet) and eat snacks in the parks. Also had delicious meals in the foodcourts in the Malls. Then in the evening we would eat in the villa, either a good meal or bits and pieces.

In 10 weeks time we are going again and this time our daily budget is $ 200 a day. The girls, now 12 and 15 have a $ 30 a day budget.

We plan on eating out for breakfast every day, we have looked and printed restaurants for meal deals and there's WalMart for eating in the villa.
In general we budget:
$ 45 for breakfast (we're not spending that though)
$ 60 for lunch/dinner
$ 15 for parking
$ 80 for buying stuff
We know we will have money left over. Still if you go and eat for $ 100 or even more per day just for dinner each day, then you know you need to budget more money. It all depends on what you plan to spend.

We also by lots of stuff but cheap at flea markets, WalMart and sometimes a sweater in the parks.
Have fun!!