I had the same question, when people found out I was having a DW, most people alread said, well since it is a small event, we can do a bridal shower or something else for you. I also got questions from friends and family, like where are you registered since you are doing a DW so we can do something for you.
I think some people understand the concept of DW wedding and don't get offended if they are invited to a shower, but just want to celebrate with you in some way.
But in the end I will leave the shower situation up to my Bridesmaid and friends.