Many of my friends have had co-ed showers...the ones that have gone over better with men are more of the BBQ/backyard hangout type of events with a brief break to open presents. I would minimize all the frills, decorations, and most of the games with a co-ed shower. My husband has grumbled about all of them, but he grumbles about most social events- as long as he has friends there and there is food, he is usually a happy camper at the end.
That said, I'd talk with your host to see what type of shower she has in mind and what she can accommodate and how many people she's prepared to host. Inviting spouses/SOs doubles a guest list, so you might need to reduce the number of people you invite to account for the men.