How to setup an iPad for a child

I owned an iPod 20 years ago but have never owned anything else Apple. My child received a new iPad for a gift. I can log into my Apple ID account through a browser on another device but while setting up the iPad for my child it is stuck in a two-factor authentication loop. I log in with my ID and it texts me an MFA code but after entering it sends me another one and asked me to enter it and it appears to be stuck in a loop. How do you set an iPad up for a child?

[Re-Titled by Moderator]