As everyone has said it really depends but I'll add that if you are getting one of those special crazy expensive drinks in a gimmicky glass you can ask for the drink in a regular glass and it will be cheaper.
Also, at certain quick services you can usually ask to skip the side (if it's something you don't eat) and they will take off $2.00.
Character meals and buffets are super expensive, usually for not the best food, although I don't even know how they are handling them right now anyway.
I went with just DS (8 then) two years ago and this is what we spent, roughly:
Breakfast at POR was several ala carte items that we split (i.e. fruit salad, cinnamon roll) with chocolate milk for him and cappuccino for me ~ $23.00
Average quick service for the both of us ~ $25.00 - $30.00. Sometimes he got a kid's meal, sometimes not.
We're snackers, so there was always at least a Mickey pretzel for each of us and maybe a frozen drink or two at the pool. I'm sure that came to $40-$50 a day but it often replaced a meal.
Our sit downs were cheaper (i.e. The Plaza in MK) and we didn't do many.
Overall we spent $110-$150 a day total depending on poolside drinks (obviously only mine had alcohol but they are still expensive) and whether we did a sit down.
We could have cut that down further if I had brought breakfast for the room.