S.W.
I think you have it all covered. I probably would not Skype for the simple fact that she might really want you there and you can't be there for her. Besides she is going to have a blast with the grands and may not even miss you if they keep her going for the next few days. Grands have a way of doings a little bit different than mom and dad and that's fine.
Go, have a great anniversary, happy birthday and happy everything else. Enjoy being a couple on their belated honeymoon. Take in the moon if it is out and get to know each other again. Darn it, now I want to come along and enjoy the scenery.
the other S.