How to create an email alias for a group of people?

If you want to create a mailing list where everyone on the list can send to everyone else on the list, you should try google groups.

If you just want a list so that you can send an email to a bunch of people at the same time, it's even easier. In gmail, go to your contacts (in the new theme you click the arrow next to the word Gmail at top left) and select the contacts you want to add to your list. A button will appear above your contact list, click it, then click "create new" and name your group Parents or something.

Whenever you want to send email to the group, just type "parents" in the the To field and it will be sent to the whole group. (You can use Bcc to avoid sending the whole world everyone else's email address).

Google Groups are good for this. People can be added directly, request to be added, and control frequency of message/email delivery themselves, or the admin can do it. The group itself can be flagged as private, public, etc etc.