Cannot access my child account on iOS

[Jsonconverter]

Google forced me to migrate my child's account for its services.
Now I am trying to understand How I am to allow him to use the Fitbit software that we paid for.

Is it correct, that I need to sign into his Fitbit app on IOS with my user identity ? 
-This seams a bit weird to me, and not really best practice in terms of Cybersecurity..

Please fell free to share any detailed guides, as the google help knowledge spaces are very shallow as to the process. 

Best regards
The father considering Apple watch for his child

Moderator Edit: Clarified subject

[Jsonconverter]

Guidance from Google here : How do I manage my child in the Fitbit app? - Fitbit Help Center 

[LizzyFitbit · Accepted solution]

Hi there, @Jsonconverter.

Thanks for sharing these details and the link you found regarding child accounts. Just a heads up that because parents are the managers of child accounts, they will be prompted to log into their accounts before switching to the child view.

I appreciate your feedback! If you want to suggest an easier way to view your child's stats, posting the idea on our Product Feedback board is the best way to get our developers' attention.