While technically against TOS, I would take it with a grain of salt. Niantic has sponsored people with multiple accounts and even Trainer Club who has a collaboration with a 3rd party auto catcher which is against TOS. If you want to be 100% safe you can make another account but it'd be hard for them to prove that sharing an account with your kid is a detriment to the game. It's more of an umbrella to stop people from sharing the account in different locations. If you watch videos of people who attended, you'll see tons of people with multiple devices and accounts despite that being against TOS but at the end of the day, that person paid for a ticket on each account so they probably don't care.