First, we don't know exactly what D23 wants, but since her BF invited H, you'll have to go with it.
I don't think I'd ride with him. It could well be that you don't want to be tied to his schedule for returning, if nothing else.
As far as the friend you had invited, I'm sure he'll understand when you tell him why you had to uninvite him. Make sure he knows that the day is for D and her BF, and you don't want to cause any drama. He'll be ok with that, I think.
