Bill,
One way to get around the limitation is to have them sent their
emails not to the group but to a custom Gmail (or whoever) address
you create, which you have already added to the group and have set
up custom forwarding (of their messages only) to the group
address.
That will allow their messages to post to the group unmoderated
but won't give them access to the group's pages.
Cheers,
Christos