I'm pretty sure that the settings are only "not safe for" XYZ (which limits your liability, which is great). However, there is no way to discriminate to guests based on age. So I think your hands are tied related to which inquiries guests can make related to the age of guests staying. You can, of course, deny them.
I might not be correct on this!
But I put an "X" for all my listings on all children, infants, etc. 50% of our bookings are families with little kids so I'm certain that it certainly doesn't deter folks from ultimately booking.