Hey Matt,
Chicken is very forgiving. In my experience I have tried cooking beer can chicken from anywhere between 225 and 325. They all turned out well.
The key is to keep an eye on the chicken's internal temp. Your chicken is done when the breast is at 160 degrees no more. The thigh will usually be warmer, about 170 to 180. So for me... I tend to cook beer can chicken at lower temps. This allows for more time to hang out by the cooker and drink more alcohol. Cooking the bird at higher temps shortens the time and will produce a crispier skin, but I love Qing too much to rush the process. In the future you should consider brining the birds also. I will leave mine in the brine overnight. Since you are cooking today you don't have that much time. When cooking at lower temps, I recommend crisping the skin directly over hot coals when you remove the birds from the cans. Just a minute or two on all sides. I do this because the skin turns out a little rubbery from cooking with all wood at lower temps. If the coals are blazing the skin will probably tear quickly so be careful, let the fire cool down slightly. Lastly, don't forget to let the birds rest for at least 20 minutes before "digging in".