250 chicken thighs 2 pork shoulders and 2 butts

I just did a mess of drumsticks on my drum, I read on thepickledpig.com that you want your drum up to about 300* for thighs and drumsticks. I put my drumsticks on when my drum hit 250, had all of my intake vents wide open THE WHOLE TIME. By the end of the cook my drum was running about 325*. The total cook time for ONE rack (all my drum has right now) was an hour and a half. I had 8# total on one rack. If it were me I would dedicate one drum to your the butts and shoulders, see if you can get them all into one. With about two and half hours before party time fire up your other two drums and see if you can get all your chicken on the other two drums. If you can't, get your butts and shoulders done, foil wrapped, towel wrapped and into coolers, they will hold for hours like that, pull them later. Then fire up all three drums for chicken and let your butts rest while chicken cooks. Don't know if any of this helps, good luck.

How many lbs of chicken? I fit 8# on one wrack, three drums with two racks each makes for six racks or 48# of chicken (roughly) you could do on all three drums at the same time. If that is enough, do your shoulders and butts, let them rest while you take a couple hours for the chicken. If you cooler them real good the butts would be okay, I bet they would pull apart with sporks by then lol.

I cook thighs at 350 for 35-45 minutes and they come out awesome. That's alot of chicken you are doing and your guest are going to want to get at the food so it better be ready. Good luck.

I'd cook half on the drums and the rest on a grill, in batches to order. When is the event?

You can easily increase the number of grates for chicken (and ribs also) with some of these:
http://www.foodservicewarehouse.com/thunder-group/slrack1734/p366851.aspx

I use them in my WSMs. They are good quality and very reasonably priced.

The simplicity of this expands exponentionally with the number of pieces U need. I have always cooked chick as follows:

Meat side down 5-10 min until the skin is nice n brown. Turn 'em and let 'em finish - 185 for thighs - 165 for breasts.

I use a meat probe for temps.