Wedding invite wording.....HELP??

Hey Ladies, ok so I started to revised my STD address list for the wedding invites, and I came across a couple of questions,and wanted to hear what everyone thinks....

In regards to the 'and guest', if you know their last name, do you need to write it...hence if you don't know it do I need to get it?? and does this apply for both the outer and inner envolpe?

Example
I know the man lets say, and only the girlfriend's frist name

(outer)
Mr. John Smith and Guest

(inner)
Mr. John Smith and Jane

I hope that makes sense!! Any thoughts??

Call and get the last name.

You'll need it for the invite later anyway...

If it's a true 'and guest' situation like you're just allowing your person to bring an unknown guest of their choosing, then the outside envelop will only have your guest's name. The inner envelope will then say, Mr. XYZ and Guest.

If it's your friends significant other or whoever that you're sure they'll bring then by all means try and find out they're first and last name, I always appreciated that when I was dating FH and he was invited to his friends weddings. We were together 3 years and I hated seeing the invites written as Mr. FH and guest. I mean come on, I'd met them a million times, all it would have taken was a phone call or email to FH to find out my last name if they really didn't know it.

I've been going to family and friend events with my FH for almost 3 years already, and although they know his full name, I still get invites that say 'and guest'...he gets upset, but I say who cares.

If you know the person's first name I say that's better than 'and guest' at least for the STD