Most mushrooms are mainly water so become an unappetizing mush. They'd have to be very dry and fresh for freezing to be anywhere successful. So don't wash them. They'd only be good for cooking. Personally I'd do as I said in my first post.
Or make some soup now and freeze that. Buy more mushrooms for when you need them next week. By the way, how do you know that you're going to "need" mushrooms next week?
I need mushrooms cos I'm going to be making a yummy lasagne and last time I made it I did find the fresh mushrooms, fresh peppers and onions made it so much nicer than the frozen stuff.