You can add your child (s) as participants in events by creating an own icon for them.
After creating a separate kids icon, you can change between your own and the child's account.
1. Register your current account
2. Create an invitation and send it to a second email address you use
3. Log out of your current account
4. Start TimeTree as a new user
5. Register your child as a new user with their name / icon and register their account with the email address you sent the invitation URL to in step 2
6. Tap the URL you sent in step 2 to join the calendar
7. Log out of your child's account
8. Log in back to your own account