how much is enough?

Welcome aboard.

Are you planning to smoke packers or flats?

For starters, I'd plan on 1/2 lb per person, of finished brisket. You didn't mention any other meats so I assume brisket is the main course.

Packers will yield 60-70% after trimming/smoking, depending on the amount of fat cap & kernel fat you trim away. Flats will yield about 80%.

Push come to shove you'll need 15 lbs of meat. Two packers in the 11-12lb weight range should do it, or 3 8 lb flats.

I plan on 50% for briskets. Unless you do a lot of them, that's a good average for planning. No problem with having a little extra left.

Ok thanks. I was figuring on maybe 15-20 lbs before smoking, so looks like I was pretty close. There will be chicken wings also, but main meat will be brisket. Would rather have leftovers than not enough for sure. 1/3- 1/2 lbs. per person probably sounds about right. Some will eat more, some less. Thanks guys.

Hey, get more, use full packers and make some burnt ends. Definitely worth the effort. Check out B.E. 101