Was it windy when you were trying to smoke? The low outside temps should not affect the smoker's ability to reach 225Â° - 250Â°. There are people here who have posted threads of smokes they have done in single digit temperatures. However, even a slight breeze with temps in the 40s will raise havoc with the smoker temp. You may need to construct a windbreak.
Maybe not quite that much wood but you get the idea.
It's always good to have an extra bag of charcoal on hand. The other thing you might do is do some practice runs to get the feel for how the smoker runs. Just light it up with no meat in it and practice regulating the temps. You can learn a lot about your smoker this way without the pressure of people waiting on dinner.
You may also want to practice with ribs if you've committed to smoking for a group. Try the 2-2-1 method for babybacks and you can adjust from there. The great thing about practicing with ribs ahead of time is that you get to eat them.
Hang in there and keep asking questions if you need to. The smoker in the above picture would have been sold long ago if it wasn't for the help I received from the members here.