You'll be Ok. Remember how you worried with your first butt only when it was done to think back and realize there was no need? This is the same thing. The meat cookes itself, we just tend the fire or plug in the cord.
Personally, I would do both ahead of time, like you were proposing for one. Smoke it give it a good rest without worrying about the clock. Pull it, hit it with a little finishing sauce (Chef JJ's is total awesome sauce), so it can soak in. Then bag it & tag it and in the reefer it goes.
Then the day of the party, pull it out, put it in the crock pot, check the taste, adjust, cover ..... you got to sleep, shower, clean clothes, no stress, and you can enjoy the food with everyone else and act nonchalant like its just another thang for a pit master.