Invitation questions

My aunt is doing the calligraphy for our invitations and
I'm trying to finalize the list of addresses and I suddenly realized how clueless I am!

We don't have inner envelopes, so if I'm inviting someone with a guest, I put it on the outer envelope, right? Do I write 'and guest' or '& Guest'?

Also, should I ask my aunt to address the RSVP envelopes too, or did you girls print them/use labels?

TIA, I'm freaking out here!

Since you are not having inside envelopes I think I would:

Mr Mike Jones and Guest
1313 Mockingbird Lane...

And I would say just get a rubber stamp for the return. Better yet, if you have not ordered the envelopes, get the return pre-printed.