How can I remotely manage website access on my child's MacBook?

I have a foster child that I support but does not live at my house. I have a MacBook Pro for them that I need to lock down as much as possible. I've limited the screen time and probably won't need to change that remotely but I need to control outside communications if possible (at risk youth). Things like snapchat, texting, calls, etc. Any suggestions on how to proceed? Any way to do remote controls settings ?

I could give their guardian an admin password to allow specific downloads but not sure if I should blacklist specific websites (not knowing all the possibles) or do a whitelist which would require the admin to approve every website.

I thought of adding them to our family apple account but if they create their own, what would they be able to access?

[Re-Titled by Moderator]