It is SO AWKWARD when little kids want to look at my comics. It wouldn't be so bad if CosPain was the extent of my work, but I also do horror and mystery comics that are very much not meant for younger audiences.
I have done basically this exact maneuver when parents have approached my table wanting to buy a mature comic for their child. Much of the time, I lost out on the sale, but the parents always express their appreciation for my actions. It can be tough keeping track of what your kids are exposed to, and I'd rather help a parent with that and lose a sale than sell a product that will lead to problems for someone else.
As for unaccompanied minors coming up to the table and grabbing stuff, I got much more comfortable with telling them they couldn't peruse certain comics after making rating labels for the display copies. I strongly recommend having these on your books.
Rock on, guys, and never stop drawing.