Ok i wasnt going to comment but I think i need to. To be honest I think you are taking this way out of proportion and I have to agree with the other married ladies here, like Andi, Rachel, Niki, Ann and Carly.
I really doubt it will take away ANYTHING from your wedding. Especially b/c you mentioned that barely any of your guests really know them. So for one minute on the day before your wedding some ppl will congratulate them but this will hardly steal your thunder. I dont mean for this to sound so harsh but in the end - on your wedding day i guarantee it will be all about you and their engagement will have ZERO impact.