I'm sort of interested in the same thing, but I think to get a la carte service and nice, varied food, it is so expensive that you probably wouldn't save much compared with doing it separately.
We often get hotel B&B (I don't mind and quite like a hotel buffet breakfast, but I like to eat out in outdoor restaurants with table service for other meals) and have a big late breakfast at about 9 or 10 am, lunch quite late (2 to 4 pm, but we normally go to Spain, where this is the normal lunchtime for Spaniards).
After that, I don't want more than a tapa or two in the evening, so aren't buying 2 full restaurant meals a day anyway. We don't eat out all meals and sometimes will just have an ice cream for lunch and have a bigger dinner later on, or buy bits of cheese, ham, bread etc from the supermarket in additon to lots of drinks and some snacks, so that cuts the cost a bit.
Are you eating all the meals you buy - DCs eating all of 2 restaurant meals a day, plus breakfast? If food is being left, maybe another way to cut costs, in addition to the suggestions above, would be to order 3 or 4 meals to share between you all?
Or how about self catering with some eating out, plus easy supermarket food (barbecue, pizza, roast chicken and salad, bread, cheese, olives etc)?