If you have extra luggage space, you can pack snacks like goldfish or other crackers, cereal bars, granola bars, stuff like that.
You can now order from Safeway for delivery, and although I've used Garden Grocer many times, I found the prices to be a bit better at Safeway (and I'm going to use them for our next mom/daughter trip in March). I'm ordering wine (I have my priorities!), 2 cases of bottled water (I don't care for the tap water in Orlando much, and we like to have a bottle next to the bed and to make coffee with), a 4 pack of Starbucks double shot light (DD likes them sometimes), a few bananas, some juice, cheese and crackers (late night snacks or by the pool), one bag of chips, disposable coffee cups with lids, good ground coffee, and a bottle of creamer she likes. I bring a travel coffee maker (we're staying at a value resort), and can get sugar at the food court. Oh, and chocolate muffins for her & bran ones for me from the bakery. That's what is in my cart right now.
I do prefer protein in the mornings, so I may add some deli meat. We aren't big breakfast eaters, but like a little something with our morning coffee.
When the kids were little, I would have things like poptarts too (no they're not healthy, but it's vacation). Also I'd add soy milk (DS is allergic to milk).
If your kids like yogurt, you can have that too for breakfasts. For light lunches, you could get a loaf of bread and PB&J or lunchmeat, and get paper plates too. It's nice to have, not so much for the savings but for convenience I think. Sometimes when kids are hungry, they are hungry NOW, and meals are so big to me even at the food courts. I always had a few healthy snacks in my purse or backpack in the parks (but I have one kid with allergies, so it was easier when he was little). And, some protein is better than too much sugary stuff all the time.