Personally, I think it can be a mistake to be too strict with your own eating as well as the kids. I am not saying go hog wild and eat doritos and every bit of junk there. Tell the kids they can have chicken, potato salad or a few potato chips, eggs, and a piece of pie. Bring a fruit plate as well with some of the fruit dipped in chocolate or a yogurt honey dip.
There is a compromise to be made that allows you to basically stay on track and feel good about the food, but not make a war out of it.
The kids I know that grew up with parents that were very militant about anything, whether it was food, religion, alcohol, etc ALL have issues. Two friends that grew up with very strict food rules are both binge eaters to this day.