Very much appreciated, Richard. Thanks. Being fair to everyone concerned is always tough especially when things change.
But dare I suggest that it might be even easier to simply admit us (in a measured calm and orderly fashion) to the room in the order of registration rather than actually assigning each person a specific seat? I suggest this since (for example) registrant #1 might not be as happy if seat #1 turns out to be located at the left end of the first row rather than in the middle. If all registrants received a ticket in their package with the appropriate numbered designation, it'd be extremely easy for us to line up shortly before the workshop in order of registration. Then say, 15 minutes prior to the start, the staff member marshaling the door admits each of us one at a time in turn after verifying our ticket and numbered place. That would put at least a few seconds between each admission and avoid a stampede while at the same time allowing folks to choose and take their seats fairly quickly. Even if you forcibly inserted a 10-second pause between each admission, everyone would still be inside in a little over 12 minutes (and a 10-second pause is way more than what it would really take.)
My apologies for continuing this beyond the seat numbering solution, but it touches on an aspect from the logistics of event planning, something I used to do as part of my living a long time ago ... and I can't help myself after been there, done that.