Membership - All Members Need Admin Approval

I am looking to have a simple way of setting up about 5 different "members" that have varying access to my sites content, all free, no paid subscriptions.

These members that register, need to get approved by our admin, before they have access to our site. What do you think is the best way to set this up? Or is it even possible with the Membership app?

Here are the questions I am asking:

1) I was thinking of having 1 public registration, and 5 hidden and the admin can add them manually to the correct membership . Is there a way to gather more information from my users during registration, so I can verify who they are and any other relevant information from them?

2) Or does the membership app not going to work appropriately for my needs?

Thank you very much for your help!