Depends... could be as little or as much as you want. However, I would say that we spend about $50-65/day per person on food (since we usually do a sit-down/character meal 1x/day -- altho, we often only eat two "real" big meals a day & snack the rest of the day,)... another $30-50 on miscellaneous and I usually reserve about $100-$150 per person for souvenirs for total trip... I know that may be a bit conservative for some people, but it depends on how often you'll be eating at a sit-down place, how many snacks (i.e, Mickey Bars, popcorn, bottled water) you buy and how irresistable you may find the Hat stand to be... or all those fun exit area merchandise shops! Don't forget the ride photos! Could be $29 or more each!
For prices of restaurants, you can check out the dining section at allearsnet.com. That should help with figuring that part out.