Often thought of the same thing. So leaving this comment here in case someone got a good solution that don’t involve big tech.
When I get the time my plan is to read up on big techs solutions, fx Google and Apple, who as I understand can give your family access under certain conditions if your’ve passed.
EDIT: And replicate their solution using FOSS / self hosting.
Can recommend calisthenics / body weight fitness. It is easy to get started, hard to get wrong and the results are the best I have experienced.
I know, reddit. But search for ‘Recommended Routine’ on reddit for a good place to start.