For future reference, start with 2 butts very close in size, within ounces not pounds. Figure 2 hours per pound multiplied by the pounds of the largest butt. Add 2.5 hours, subtract total from the time your event starts.
So if both your butts were 8 pounds, that is 16 hours + 2.5 Hours (Rest&Pulling)= 18.5 hours
Your event started at 5:30 PM so you should have put them on at 11:00 PM the night before, removing and wrapping them at 3:00 PM. Then rest them until pulling them immediately prior to 5:30
I hope all that makes sense to you, good luck on the wedding.
This allows you time to smoke the meat wrap, rest and pull it all prior to serving time.