I way underestimated the cost of food on our last trip in June. I thought we could do about $125/day total for 3 people. That's about $40ish per person for lunch, dinner and snacks. We did breakfast in the hotel. The reality was that I should have budgeted $60 per person each day. Food is expensive! We didn't do sit down dining, only quick service, but a lot of things were closer to $20 for an entrée and then drinks are expensive too. Plus snacks add up. We didn't really go in with a tight budget though, I wanted to just relax and get things we wanted and not try to cut costs everywhere. So I was ok with buying drinks because it was convenient and they were cold. But I was a bit shocked when I tallied our spending. Granted, I now have a teen boy and the last time we went to DL he was only 7 and ate kids meals.
One thing I did do often was that I would order a kids meal for me since I don't want a huge entrée. I like to save room for snacks and I don't want to feel stuffed full and then go on rides. So smaller amounts more often works better for me. So that saved a little but it didn't make some huge dent.
I would recommend looking at the menus online of where you want to go and using that to budget.