But in my mind, I don't think any of us (or I) will even suggest our kids, someone who is known, a close relative or friends who is not adult yet to join the forum.
You will be surprised the kids will find the forum by themselves. This is possible that they may use some bitcoin keywords in their search and they will be redirected here. They will sign up with unknown username and keep interacting with you here
If discover the account and see s/he is really into learning bitcoin and the technology then I will feel proud for them but if I see they are building the account just to earn from the signature campaign then I will be disappointed. I will like them (suggest and help) to learn a skill and educate them first before even thinking to earn some pocket money. When he will master a skill then he will never have an issue with money.