Quote Originally Posted by M. A. C. Newsome
With older kids, they might be more open to having you come up and talk with them. But just check out mom and dad and see how they are. If they are open to you coming and giving their child an educational experience, you should be able to tell. If they look like they just want to get on with their shopping and get home, I'd leave it be.
And if, as in the the situation described, the parent can't even be bothered acknowledging their child's comment, then I'm guessing that parent isn't too interested (at least in that moment) of giving their child an educational experience. So just move on.

Kevin