I have found that most kitchen chairs are very easily cleaned, the fabric used will likely be a material that easily cleaned , even perhaps just wipe able., now dining chairs are a different matter.
I cleaned 80 chairs in a restaraunt yesterday, all very easily cleaned and just part of the seating area upholstered, a simple h/w/e with very hot water did the trick , no pre spray , no aggitation just an extraction. £3.00 per chair done in 2 hrs.
I would suggest you tell the custy you wish to test clean one, discover how easy/difficult it may be and look for any adverse effects then go from their.
geoff