Folks I need some advice. My HOA is planning a July 4th neighborhood BBQ, I've never hosted an event before. We're estimating 100-150 people.

1.Is it better to do a whole hog or just butts?
2.COSTCO, or Meat store or grocery store for the best price/quality for the meat?
3.Any suggestion, advice, or otherwise?
THANX IN ADVANCE FOR COMMENTS
Dick