Mixing Chicken and Pork is not a great idea for a few reasons:
- Cross Contamination: You do not want semi-raw chicken drippings mixing with the Pork unless you plan on some quality time in the bathroom!
- Flavor: Poultry picks up smoke flavor quickly. I would only use one small piece of wood for two chickens, but 6 oz of Hickory for Pork Butt. If you combine meats one of the two will not come out right.
- Texture: Pork Butt needs low & slow temp like 225. Poultry has no tough connective tissue and the skin will turn out best if you pre-heat your smoker to 300 degrees or higher before adding the chicken.
Whole birds (around four pounds) only take a couple of hours at higher temps. Why not cook your pork, foil it in a cooler, and then cook your chickens? I'm sure the guests would like to see them coming out of the smoker.
Hope that helps!