I agree with the other posters. As the parents of a 7 & a 4 year old, my DH & I have taught our children that it's ok to respond to adults they don't know as long as we are with them. Often, this situation arises when it's an adult from church, a business client, etc.. that the children don't know. Both of my kids are very outgoing and "never meet a stranger." I can so see either of them striking up a conversation in line. However, they have both been instructed NEVER to talk to a stranger when they are without DH or me. But, I also know that at their ages, there is no feasible reason for one of them to be without a parent. So that shouldn't ever be an issue. I do appreciate the OP's sensitivity and concern about appearances. It's a gentle reminder to all of us parents that we should always be vigilant, even at the happiest place on Earth.