more info needed.
Are you getting the free dining package?
Are you drinkers?
Are you shoppers?
If you are on the free dining plan, you won't need much for food if anything. It's a LOT of food. Here, I would have them budget for any alcoholic beverages they might want and maybe $10 per day over that.
There are lots of tempting shops, especially at Epcot. You could easily go nuts but they can determine how much they want to spend on souveniers. Remember, it's not cheap!
Pretty much everything in the parks is free (I assume you have your passes) . But perhaps a night at Pleasure Island or the Boardwalk?
Hope this helps!