I have heard of briskets getting done in as few as 6-7 hours and as long as 15 hours, pork butts can be nearly as long on occassion. To answer your question, yes, it is likely that you can feed folks by 6-7pm by starting at 5 am... Is it a gaurantee, no! If the temperature stall period seems to go on forever you can foil and increase cooker temp to accelerate things without burning the meat. Others will chime in and give their opinions/experiences...
Bo Compton in Mesa, AZ, KCBS CBJ
Weber Ranch Kettle, BDS Mega, OTS x 2, Weber Platinum
18.5 WSM w/Stacker from ProQ, 22.5 WSM, Reverse Flow Lang Clone 80 butt capacity mounted on 25 foot trailer with attached awnings
LFSA RED Thermapen,
And 1 2010 Victor brand Hot Dog Cart