And the wedding stress has finally got to me!
I had to have the same convocation with my dad! We are only having 12 guests at our wedding. it took a long time to make the decision on whether to invite him. I sent him a message on fb (I know - cheating but we live over 300 miles apart!) I told him our plan, small and family only and mentioned prices at the hotel the night of the wedding and he asked whether that was a double or single. So I had to explain, due to budget and that fact we only want a small wedding, that the invite was only for him. He was fine with that, not sure how she reacted! I honestly thought they had split up as he is now living by himself so hadn't thought it was going to be an issue.
sorry, this doesn't really help with your problem. I think my dad was just grateful for his invite after our relationship over that last few years!