I have done two pork butts in the past five months. Each was 8-9 pounds, uncooked. I prepared it for just my wife and me. The two of us had one huge meal (we over-ate) and then I froze seven 12-oz bags (I weighed them) each of which will make two really large meals for two. Thus, I got eight meals for two (sixteen servings) from eight pounds of meat. These were generous portions, and we only had slaw and drinks with our sandwiches. If you are serving other sides, you could get more than these sixteen servings from eight pounds.
So, using my experience with these two smokes, starting with thirty-three pounds of meat, I think you have enough for sixty-six people, and should therefore have no problem feeding fifty.