lots of ribs

You can't cook enough ribs in one time in a 55.

For 100 people, let's say you give them each 2 bones and LOTS of sides. With one bone wasted you get about 12 ribs a slab (spares). So 6 people to a slab (3 is more likely, but we'll go with the 6)

6 into a 100 is about 17 slabs.
3 into a 100 is about 33 slabs.

So somewhere between 17 and 33 slabs will be needed.

See the math? So the problem is first to figure out how much you want to feed. Just ribs, sides included, etc? The figure out how much for each.

For 100 you could easily do pulled pork and feed them easier. Ribs for that many gets to be a lot of work.

Thanks. I will have a lot of sides as well. This really helps. I appreciate it.

Since I'm doing a dry rub can I smoke some before hand, maybe 2/3 done thwen finish them on a charcoal fire?
Full menu is ribs of course
Tri-tips
Beans with 1 lb of hamburger for each 1 lb of beans, probably 12lbs each
pickled pigs feet salad
green salad
Potato Salad
french bread
watermelon slices

I may change the tri-tips to beef brisket after reading some of the comments here.

Are you getting paid for this or volunteering your services? I would never volunteer to fix that much ribs!

Good luck!

Volunteer. I also have three friends volunteering to help me. My brother does great things for me too. I'm not good enoough to get paid. Boy I hope this goes well.