I'm caught in the middle of my mother and stepmother

This would be your opportunity to throw a fit to your mom. and I don't mean that in the bridezilla way.. but if that's what happens so be it. You take them both out at the same time to see your last few choices.. in between, rotate between mom and stepmom. otherwise, tell them too bad, this is what we're doing. this is the time to throw in "It's my wedding!"