I've done the overnight cook. I don't know if I will do it again, unless necessary...my night's sleep was basically: sleep, wake, check bedside thermometer, repeat for what seemed like every 30 mins thru the night. A worried sleep is not quality sleep, I found. My PBC runs cool, so I have to keep a closer eye on it than most, and I have had the charcoal burn out on some butt cooks. That kept me worried all night since I had promised pulled pork for my fathers bday party at noon. So...if you are confident in your PBC, you can do it.
I always use the grate, wrap or no wrap, to avoid the meat from falling from the hook (pulled pork cook #1). I don't see any advantage to the hooks for pork butt.
I would pull the meat at home and keep it in a cooler. Pulling it at home lets you pull it when it is hotter (easier), remove the excess fat pieces out of sight, and add a little seasoning and toss (if you prefer). Then at the picnic it all looks like wonderful magic. Good luck.