Spraying thoroughly--top and bottom of the foliage--with soapy water every morning for the next three days should get rid of about 99% of them. If you have access to worm castings, applying them thickly to the soil will make the remainder much less of a problem with your friends.

or go for a systemic insecticide that should protect the plants for a few more weeks when any hidden eggs hatch.

It might be better to wait until the following meeting. you may have more whitefly in the greenhouse so you may need to treat that too.

Thank you Tug and Seaburn . . . it seems all is not lost just yet.