Can you tell me if it is customary to invite the father of the bride and groom to the bridal shower? What about the groomsmen? Are they allowed to attend the shower?
No it is not customary to invite the Father of the Bride and Groom. This includes the groomsmen as well. That's the cut and dry answer. Let me add this though. Today weddings and the events surrounding them are changing and evolving to reflect today's modern society. So in my opinion I believe it's perfectly fine as it reflects our times today.
That being said, if you'd like to be creative and include these individuals making it a coed shower then by all means do so. Just keep in mind the dynamics of the shower should change as well. Female oriented games that are generally played at showers might have to be adjusted or not done at all.
You should also keep in mind the sensitivity with the opening of the gifts. The men may not want to sit in on that particular part of the soiree. I’m not sure how well it would go over with a father having to see his daughter open box after box of ladies lingerie (smile).
I hope this helps,