Hi there,
I did the same thing with my kids a few years back - they were 16 & 17 and it was to be our last 'family holiday'. We were only in Orlando for a week and did 8 theme parks in 7 days LOL!! I ran it like a military campaign - no sense in lolling about in bed late, these holidays cost too much and we were there to make the most of it. We found an excellent restaurant (one of a chain in the Orlando area, I think they were called Ponderosa or something like that) and every morning we went there and they had a fantastic buffet breakfast, (ranging from cereals, fruit, fry ups, pancakes, toast etc etc) all you could eat for $5. Well, you can imagine, with a man and two teenagers, we got our moneys worth!! Then during the day we would have a snack (burger or similar) a couple of ice creams (too much to do in the parks, to think about eating too much) and then in the evenings, we alternated between a cheapy meal at MacDonalds (hate them over here - but soooo much better over in the US) and a decent meal at a better restaurant. I go to Florida regularly now without the kids (Gulf Coast - beautiful!!) and we roughly base our food costs at �20.00 each per day - that tends to cover shops at the supermarket (because we always stay in self catering - not that we 'self cater' much!!), snacks, ice creams, booze and a nice meal out every evening. Like you, we never go too luxurious but it is nice to spoil yourself while on holiday and there are plenty of good places to eat in Orlando that don't cost the earth!! As for souveniers, well that's down to how much you want to spend and believe me the temptations are many and varied - so depends how good you are at resisting temptation!! LOL!!
Have fun!!