family sharing approve spending money

I don't think I'm understanding the family sharing correctly - it seems that you either can ask to approve apps installed on your kids iphone, or not approve.

Which would be insane - I can't think of any parent ever who would want either of those options?

I, like probably every other parent out there, just wants to have control over my kids _spending any money_. Anything they can do for free is fine by me. How do I set that up?