I am making a bridal shower cake for a Saturday. Tuesday will be the only day I have to make the cake. Can I decorate it and then freeze it? I am only using buttercream frosing. Or how should I go about this?

Yes. Box it up and wrap it with plastic wrap and then foil. Friday night take it out and let it thaw in the wrappings. That way if condensation forms it will form on the wrappings and not on your beautiful cake.