How do you ask people at 3 weeks before if they would like to come to your wedding - fortunately we had some family that could not come so it made some room for more friends.
Maybe call them and flat out say "I'd love for you to come to our wedding. I know it's short notice, but I want to mail you the invite and let you know as soon as possible." I don't think you need to get into the details of why you are asking so close to the date. You'd be surprised, they mayjust jump for joy and see it as an honor that you asked no matter how much - or little - notice you've given them. Go for it.
I would just put the invite in the mail ASAP and hope that they will be able to make it on short notice. If the RSVP date has already passed or is coming up really quickly just take out the response card with the date on it and replace it with a generic card asking them to RSVP ASAP. I wouldn't call. I wouldn't want anyone to know that they were b-listed. And if someone called me and basically told me that I was second string I would decline the invite.
Maybe call and ask why they haven't rsvp'ed yet since the deadline passed? I know it's sneaky but post office accidents happen and they then won't realize they are B list invites
I don't know, if these are friends of yours and you tell them now that some family declined you have more space they should understand. I would! You know your friends best. I had a few people we invited late in the game and they were SO happy to be invited and they all came. We spoke to them all first and then sent invites so they had them.
I would say that we had a limited budget for our wedding so we had to keep our guest list to a minimum, some people backed out at the last minute and we thought of you immediately. I know it is short notice but we would love to have you attend our wedding....
Could you blame it on your family? I would say something along the lines of "My dad paid for the reception so I wasn't able to add all of the friends that I wanted to on the guest list. A few family members backed out so I now get to start inviting a few friends. I'm so happy that I get the chance to invite you now and hope you can make it."
Re: Last minute invites - how do you ask?