As others have said, don't worry about it too much, it will go smoothly.
I'd suggest using the Minion method, it burns slowly and holds temperatures well. Usually I'll try to fire up about an hour - hour and half before I want to stop paying any attention. After that time, its usually fairly stable in terms of temperature and you can leave it unmonitored. I've never had any really bad incident leaving it unmonitored, the worst I had was in the morning once the temperature was a bit low as the wind came and burnt up a lot of the charcoal.
If you have a Maverick wireless thermometer they are great for keeping an eye on it without having to pay attention. Set a high/low alarm and forget about it.
Again, really don't sweat it, it's pretty hard to mess up, butts are resilient. Make sure to have plenty of beers and enjoy!
Daum