How to address an invitation to girlfriend and family

[Gamom3]

I am sending out graduation invitations and I am not sure how to address one to my ds's girlfriend and her family.
Here is a little bit more confusion. Her mom is living with her boyfriend..which we know as well..we would not invite, but since she is living there how do we address that as well?

[unsinkable]

The best I can come up with is:

"The Smith Family"

If mom's boyfriend isn't named Smith, he ain't on the invite! ;)

[Carol in Cal.]

One to "Miss Girlfriend".

The other to "Mrs. Girlfriend's Mom and guest" or "Mrs. Girlfriend's Mom and Mr. Girlfriend's Mom's Boyfriend." Of the two, the second is more inviting. The first is more 'We don't really want to acknowlege your relationship,' and might anger some people. So the second is preferable unless you feel the need to make a disapproving point. And I would argue that the place to make a disapproving point is not in the context of inviting someone to something.