I'm with Bobby on this. If I've got my smoker fired up, I fill it. Pork shoulder, whole brisket, and spare ribs. The ribs come out first, naturally (about 5 hours), while the rest can take 18 to 22. Most gets portioned into 1.5 pound lots, vacuum bagged, and frozen.
If that's a 7 pound pork shoulder, bone-in, I'd get one more for sure. If there were 9 of me eating, and that was the only meat, then one 7 lb bone-in butt wouldn't be enough. Considering what else you're serving, it would probably be enough though. But why take a chance? You can always split up the leftovers and send them home with your guests, or package and freeze them in convenient sizes for your own family.