Yikes, I’m so glad you asked, coz it sure seems a distinct possibility, though I haven’t been able to test it out (or I should say I tried but haven’t succeeded yet…)
To back track a bit, if you mean “Family Sharing” (iCloud storage, apps, music, etc.), indeed all of my parents’ iToys are on my family sharing plan.
But it never occurred to me to ‘control’ their app use and purchases under Family Sharing, by setting them up as ‘children’.
Instead, I have their Apple IDs set up as bona-fide Adults under my Family Sharing plan:
However, I did set all their media and purchases to my Apple ID from the get go, i.e., they wouldn’t even be able to download any apps let alone make any in-app purchases, unless they could access the App Store and iTunes using my Apple ID.
Having said that, I just went into Family Sharing/Ask to Buy/Create an Account for a Child as follows:
NB in the next step, “…until the child is at least 13 years old.” (I’ve no idea what happens when the child does hit 13, or when a Child Account is set up for someone older…)
But for some reason I couldn’t get through this next screen despite entering all the correct info :
Instead I keep getting an error message, asking me to try again later… Perhaps you or someone else might have better luck and could share your experience there?
In any case, that particular “Ask To Buy” option under Family Sharing certainly seems promising for us here🤞
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Separately regarding cellular plan, as opposed to Family Sharing @ Apple. My parents’ iPhones used to be on my cellular plan, until T-mo offered the 55+ Unlimited everything plan at $60/month for 2 lines on auto-pay. (I believe it has gone up to $70 but still an excellent deal.)
I sure hope all this isn’t unnecessarily complicated. I figured that if it helps even just one person, it’ll be worth it!