We found these really great invitations, but they don't come with an inner envelope. I'm actually really happy with this because I didn't really want them. But now I'm having a hard time with how we make it known to some guests that they can bring a plus one. There aren't many so it's not too much of a headache, but there are some family friends who we would like to give them an option to bring a guest. I know that you're not supposed to put "& Guest" on the outer envelope, but where would it go?