D..
Well, if you don't invite them, they might think that they are being left out. It's kind of like being between a rock and a hard place, quite frankly.
I think that someone (the groom perhaps) should make a call to a representative of the family and say "Susie's friend would like to send invitations to acknowledge my side of the family, though she understands they probably cannot come. But she is worried that people will feel like she's pushing for gifts. What should we do? If she send invitations, do you think that you could explain that it's not for a gift grab, and we don't expect gifts from them?" If that person would indeed talk to the family, there would be understanding and brownie points for thinking of them.
Grooms showers aren't a bad idea. Tools and small appliances might be the theme. Then again, you said that they are scattered. I don't know how that would work either.
Dawn