K.J.
HI E.,
First let me say, I'm not E. Post LOL. But this is what I'd do. . .
1)Yup, put both their names on the envelope and first names on the inside.
2) I had a friend in this situation. I addressed the card to her and on the inside I wrote "Sarah and Joe". Once I got to know him better, and they'd been together a while, I addressed the envelope to both of them.
Have a great holiday :o)