sounds about right but I think you might be a little short. 2 ribs per person (13 ribs per rack x 8 = 104 / 2 = 52) I'd probably do 9-10 racks. Chicken quarters is tough to because you will only have so many pieces and everyone won't get a piece (don't know how many quarters per pound but pretty sure thats not nearly enough). I'd do about 60 thighs (cheap too). Sausage I'd slice up into thin pieces and should be fine. Thats a lot of food tbh but people will load up (plus left overs are great). I always make more than I need I hate to run out of food when I do something like this. Now if your doing the serving that should be fine (cept the chicken)if you give the kids only 1 rib. Also, people are going to want 2nds.. Really going to depend on how many children to adults if you want to serve the same.
I'd make (for adults)
9-10 racks
60 thighs (boneless will cook faster and will make life easier when cooking so many)
20 lbs sausage
plus sides
people will eat a lot if they can free serve lol especially if they are hanging around all night.
this sounds close to me ... we usually figure 1 lb per person uncooked meat which would leave a few leftovers even with heavy eaters. When I am cooking for a crowd on my smoker, I usually do fajitas ... beef, chicken thighs and pork plus toss on some link sausage & hot dogs if kids will be around. Couple packages of tortillas and a pot of beans goes a long ways. But I do like ribs, just takes longer to cook.