Newbie to smoking but hooked

Hi Cathie here from the great lake state Michigan started usi g a portable smoker last year loved so much I invested in a bigger one its a pro series smoke hollow gas smoker 36" tall 16.5 wide and 13.5 deep couple of questions I am smoking 40lbs of pork butt assuming theres 4 at 10 lbs each 2 in each 20lb package I need it for a party at noon on Sat today being thursday trying to not reheat can I cook all at once ? also when how long be for I need it would you suggest I start it and I believe I have a pretty good meat thermometer ( mavrick wireless 1 monitors the meat and one the grate where would you recommend I place it to have a close reading to all slabs of meat top bottom or middle rack also how would you place the meat in this situation? Thanks in advance