It would be nice to have multiple identities/accounts on one email for parents and families.
A lot of kids that are ready for Duolingo aren't ready for their own email. It would be nice for parents, especially those who homeschool to have that option.
What most parents in this situation do is create email accounts for their children but don't give the children the login information to the email accounts. That way the child can have a Duolingo account and the parent can monitor their email (have email notifications enabled on your child's Duolingo account).
Another alternative is to use "sub-addresses", if your mail provider supports them.
email@example.com for the parents account, firstname.lastname@example.org for the first child, email@example.com for the second child.
As far as Duolingo is concerned, firstname.lastname@example.org, email@example.com and firstname.lastname@example.org are 3 different e-mail addresses. As far as outlook.com is concerned, they all point to a single mailbox.
Different mail providers use different separators (+, -, ., #, maybe others) for indicating a "sub-address", but some mail providers don't support the function at all, so you'll have to check whether (and how) it works for your mail service.