They are absorbed with the wedding bullspit, and thoughts of what is inconvenient for others dont even cross their minds. You said you like these folks pretty much so I take it they are generally good folks. These things cause people to go a bit daft.
Dont get angry simply think for them. Say to them send ole boy over here after work as he only works a block from here and he can pick the dresses up.
The truth is people loose their minds in wedding planning.
Its why I avoid folks who announce they are getting married until after the wedding. Then I go back around them. They tend not to notice very much because they were wrapped up in wedding stuff. And I get out of tons of drama.

I have no faith in human perfectability. I think that human exertion will have no appreciable effect upon humanity. Man is now only more active - not more happy - nor more wise, than he was 6000 years ago. Edgar Allan Poe