A baby shower is, specifically, a gift-giving event to "shower" the mom to be with gifts. If you're going to have a baby shower, not opening gifts is rude. Asking for unwrapped gifts comes across even worse-it sounds as though all you care about is the loot and you can't even be bothered to unwrap a gift.
You have options, though. First, many friends will not be upset at not being invited to a shower, especially guys. Showers are nowhere near the significance of a wedding, and if people want to give you a gift, they will, shower or not.
Second, a larger, informal BBQ shower doesn't require everyone to sit through gift opening. Open the gifts in a section of the party location, and continue to have other activities available. People who want to watch you open gifts will, others will do other stuff.
if what you really want is a party, that's cool too. Just don't mention gifts, a registry, or anything else. Invite people to a BBQ, with no mention of baby.