I have it both ways -- my 8 & 10 year olds usually don't follow daycare rules, but my 3 year old does. When the dc kids see my older two doing something they can't (like playing down in the basement, or going outside whenever they want), I just tell them they aren't daycare kids, so they don't have the same rules. My dc kids are mostly toddlers, and they still get it. But all 3 of my own kids also know what I mean when I say "Daycare rules!". If they're doing something that I don't want them to be doing in front of the daycare kids (like climbing up the slide in the backyard), it's my way of reminding them that they need to follow the same rules as the dc kids for the time-being.
So, it could work for you. Since it's your house, you get to make the rules! If your daughter eats better in the living room for medical reasons, then let her (just watch out for the other kids trying to steal her food
). I think it's totally fair to tell the dc kids that because it's her house, she gets to eat in the living room. As long as you're consistent with the rules, the kids will accept them.