What kind of smoker do you have? If it's a WSM or even an ECB you can use the minion method and not worry a bit. Before the wedding or even that morning, get your Butt ready.
Set up your fire pan like this:
First get a tomato juice, pineapple juice or other large can and cut the bottom out of both ends. Put it in the middle of your fire pan
Next put unlit charcoal and wood chunks around the empty can with a few wood chunks in the bottom of the pan for good measure.
Start about 20 briquettes in your charcoal chimney and get them all hat and red and covered in ash
Dump the chimney of coals into the empty can in the middle and use a pair of pliers to remove the can
now, put the smoker together, load with Butt and walk away. It will maintain 225-250 unattended for 6-10 hours. I honestly think that low and slow you can't overcook a butt unless you have no waterpan between the coals and the butt, then you start a grease fire that will burn it ALL up.
You can thank me later.