Catering for 100-125

Do they want EVERYONE to get Each item? Or just a choice.

Well if it was me and I'm not smart, but thinking they would all get at least a hamburger, I would probably do Pulled Pork for 70-75 people, then maybe only a bone or 2 of ribs for everyone. Ribs will go fast. I might after sleeping on it go ahead and make enough ribs so that everyone gets at least 2 bones. (200-250 bones total) and drop my pork down to 40 people or so 10 to 15 pounds of cooked pork will get you plenty then. (all rights reserved, this in no means is probably right but it is where I would most likely start. Your experience and success/lack of may or may not be different)

be prepared to cook 125 hamburgers, 2 bones of ribs per person, 1/4 pound of pork per person. That would be around 50 pounds raw to start.

Or you could do that.

Who are you serving is it all adults, or are there going to be kids? With 3 meats you will not need more than a 1/4 per person of each one, and even that is heavy, assuming you serving sides as well.