Lunch and dinner are both served as well as snacks, and they are pretty good about trying to get the kids to eat a bit (though they won't force it). They take any allergies or preferences into account and always let you know what they ate when you pick the kiddos up. I know when we were on in March there was cheese, crackers, and fruit for snacks and a variety of pasta, vegetables, chicken, etc served at dinner. I have to laugh because DS (19 mo) wasn't eating much of anything that didn't come in the form of a cracker or a grape on that trip, but they still did their best to get him to eat.
As others have mentioned they will provide water or juice, but you have to bring your own milk in due to allergy concerns (they will refrigerate it for you), we always snagged a couple of extra cartons at Cabanas in the morning to have throughout the day (the only place they regularly had whole milk set out), and we also ordered extra whenever we got room service to keep in our room fridge.