Waiting in line to pay, a kid was trying to give me or show me his action figure...

I hate when little kids stare at me and try to get my attention. I never know what to do.

And when the parent starts smiling, I know I am supposed to interact but then it becomes awkward because I don't know if I am supposed to get into a full conversation, just smile back, or say something adult-like to the kid. There are so many options, and none are really good ones.

It would be better if the kid just stayed in his/her own lane.