Plugin for Membership

I have been scrolling around all membership plugins, but they look to heavy for me.
The WP site I build has 6 public and 6 private pages for members.
My members should not login as WP-users to avoid the WP top & dashboard bars.
The member-menu-items should not be shown publicly.
My 10 members donot pay, I could even registrate them manually.
Is splitting up in 2 sites a good idea?
What is the less complicated plugin I could use?
Many thanks for your advice folks!