If they don't want you eating what they are having for dinner, some families like to have leftovers for lunch and such. You could always bring your own food, something quick and easy that you can make at the same time, prepared food that just needs heating, or anything really that won't take too much attention and time seat from the kids. You don't have to go the entire time without eating if they don't allow you to eat their food. I've worked for families who always say help yourself to any of our food but no matter what time I'm working I usually bring my own food. There are occasions that I forget my food or didn't have time to prepare something and will use nf's food but that's rare. You could also ask if you can keep some items in their pantry, fridge/freezer that way you always have options for yourself