How Do I Add TCG Live to Child's Existing Account?

I created my child's account for Pokemon Go several years ago but now they are wanting to play Pokemon TCG Live. When they try to create an account, they are asked to provide my email address, which I understand. However, the email I receive is not very helpful:

"Your child has attempted to create a Pokémon Trainer Club account at Pokemon.com. To protect the safety and privacy of your child's online activities, we require consent from a parent or guardian in order to create an account for your child.

To provide consent and to manage settings on your child's account, you will need to create your own Pokémon Trainer Club account. If you already have a Pokémon Trainer Club account, please log in at Pokemon.com, then create your child's account. If you don't have a Pokémon Trainer Club account, please create one at Pokemon.com." 

So the issue I'm having is that my child already has an account and it linked to my account. Do I have to create another "child" for this same child? In my account, I can see TCG Live in my "Authorized Apps" list, but it's not showing up in my child's list of "Authorized Apps." How do I go about doing that? It seems silly that I'd have to add another "child" for every Pokemon game that comes out…