you're 100% correct. If it works for you 2, who says you're right or wrong? Don't let anyone say you're wrong on how your marriage is.
For all you people who think this is "creepy", it's none of your business. Besides, if ANYONE uses Family Sharing, you would know everyone in the family is on Find My Friends. My wife can see where I am anytime she wants, and I don't care at all. Why? We are a team, she's my life, and I couldn't care less what she knows about me. Marriage shouldn't be hiding stuff anyways. She doesn't care if I know too, what do we have to hide? Oh, she has access to all my passwords... OMG the horror.! I also have hers, and not once have I felt like I needed to use them.
One thing I have learned from past person experience and friends, the ones who think it's privacy were the ones who were doing crap they shouldn't be doing. Ever. Single. One.
Now to help the OP:
On iOS, it's not as easy. When my daughter was young and had an iPod Touch, I actually blocked her from safari because she was young under the restrictions. After that, I've tried apps (in think one was McGruff or something?) and I was able to control what sites she couldn't go on. Safari was still blocked, but that web browser was great, but not sure if they still have it.
Now with sharing an Apple ID, I've heard more horror stored due to this. The "oops the wrong family member got that message", if my daughter saw what my wife and talk about, the poor kid would be in therapy hahaha. I would set up the family sharing. You can also make an Apple ID for a kids though iCloud. This way you can make it so you need to approve all apps the child wants.