Dumb Question -- Addressing Envelopes to Clarify Plus 1's?

On the RSVP card you could put a line that says "We have reserved _ seats in your honor" and fill in the number for the party.

For kids, you address the envelope to "The Smith Family". Or if you are doing inner envelopes you could list everyone's name. That also applies to someone getting a guest - you could print "John Smith and guest" on the inner envelope to indicate that they are welcome to bring a guest.

If you know the SO's name, it's simple: You put the SO's name on the envelope. You can still send it to the address of the one you're primarily friends with, if they don't live together. So:

Mr. John Jones

Ms. Susan Smith

[John Jones's address]

(With unmarried couples, the names go on separate lines and there is no "and" between them.)

If you don't know the SO's name, how do you know that there is an SO? In any event, if you can't get the name of the SO, you could address the inner envelope (or the outer envelope if there is no inner envelope) to "John Smith and Guest."

With kids, you could address it to The Smith Family. Or use the names of all of them, e.g.,

Mr. John and Ms. Mary Smith

Lulu, Tom, and Susan

If you were using inner and outer envelopes, you'd probably put just the parents' names on the outer envelope and include the kids' names on the inner one. But if you're not using inner envelopes, you can just put all of them on the outer envelope.

For people in serious relationships, you need to find out their SO's name and address the invitation to both of them.

"And Guest" means the can bring anyone. It could be a friend, or a flavor of the month. But you've already said that you're not inviting people with a date if they're not in a serious relationship. So I don't see a reason as to why you would use "and guest".

I agree with putting "we have reserved __ seat/s for you" on your rsvps.