I think people should be able to pay to avoid children on an airplane. It would be interesting to see how that would work out in practice, however. What’s the airline going to do if they have empty seats and a potential purchaser with a child? Leave the seat empty? Charge the “No children” person for the lost revenue? Accept that loss and hope that advertising guaranteed no-children accommodations will, overall, result in higher revenue?
I also think it’s fine to have a “No children” restaurant, as long as the information is published. Logically, this would mean businesses could refuse to serve anyone, for any reason ... and that will never fly in our climate of forced association. But anyway ...
Actually, since airlines are charging for literally everything anymore, charge the parents for the child, not the people wanting separation from the children. Or pack all the munchkins and parents thereof in the back seats, if that can be accomplished with the computer systems.
There is (or was) one in Asheville, NC a few years back.