figuring out kosher

We have been talking with PJ about keeping kosher, and that some kosher food is milk, other food is meat or parve. He goes to a Jewish preschool but not everyone there is Jewish or religious. We went to a birthday party for one of his classmates where we knew the birthday cake would be kosher, but we weren't sure about the rest of the food. I spoke to PJ in the car about needing to ask me before he ate anything to see if it was kosher and I was very proud that he listened even when I told him he couldn't eat the pizza or cheese curls. He must be thinking about it, because he asks whether meals we are having are milk or meat (to figure out if he can have a cup of milk with his dinner.) He was also telling me about a discussion he was having with one of his classmates to figure out if their house is kosher, but my suspicion is that any answer he got was more about the other students ignorance than what actually goes on at their house.