LETS SEE.....
forgeting the chair choosing bit for a moment.. Thats your bit.
what you need to do, maybe, is once they are sat down, you ask them their names. you do this, so you can write them down on some strung cards, which you hang around their necks like a name tag.
whilst you do this, your either double writing, or using an impression envelope, to get their names within a sealed envelope.
your task is now to have that envelope arrive under the chair, or stuck on the back.
since you have cover..( they are sitting down ) Sticking it on the back isnt difficult.
and if your wanting it under the chair, then you have a larger envelope underneath, and you introduce the envelope with the name inside, into this, whilst opening it up.
( As in bank night / just a chance effects)
you're like Yoda.you dont say much, but what you do say is worth listening to....
Greg Wilson about.... Me.