DEAR MISS MANNERS: I have two amazing girls who are 4 years old and 18 months old. For the most part, they are really good eaters for me when we’re at home or at restaurants. But I have found that when we’re at Nana and Papa’s house, they are pickier eaters — to the point that I have to feed them a second supper when we get home. Should I start bringing foods I know they’ll eat, just in case? I don’t want to hurt anyone’s feelings, but I also want my kids to eat well at other people’s houses. I am aware of the menu ahead of time, but it’s so hard to know when my kids are going to object to ce…