It take approximately 10-12 minutes per person including drawing and painting time on A4 size paper, or approximately 7-9 minutes per person on A5 size paper whether I'm sketching someone posing live or from a photo.
For wedding receptions it's recommended to have guests pose for photos when they come in, which I then sketch/paint from during the duration of event and they collect later upon completion.
Numbers will be capped according to the time frame allowance if the sketches are required to be finished by the end of your reception. If the sketches are not required to be finished by the end of 5 hours consecutive sketching time then arrangements can be made to complete them in my home studio and deliver them after the event.