Our family of 4 (DH,myself,DD13 and DS11) budgets $100 per day for food. We usually eat a light breakfast, mid-morning snack. a large, late lunch and a light dinner. If you intend to eat at sit-down restaurants for every meal, you will need more.
Souvenirs can run into big bucks or they can be very inexpensive. DH and I buy very few souvenirs but I allow the kids to spend $50 each for pins and t-shirts. If you're going to buy collectibles, novelty items or souvenir photos, plan on much more money.