Xfinity ID for a new user

I created a new user as a Member on my parents account. My dad doesn't have a smart phone, so I used his gmail email as the contact method to register. I then went into his gmail to finish the registration. It assigned his gmail email address as the Xfinity ID. I did update his username, but I can't login to email as his [Edited: "Personal Information"].

I don't want my dad to have to login to comcast email using his gmail email address as the Xfinity ID. He is 80 years old and the internet is still a difficult concept.

What are my choices? My goal was to make an easier email address they can use instead of the "really long one" that is their current Xfinity ID. Can I update the username on their primary ID giving them an easier email address?

Thanks