Another option for "desensitization" would be to set up the trainer with them and practice there.

You can also get pedals that are one-sided. If I ever go clipless, that's probably what I'll do. Even wiht toe clips, I tend to start off with one foot in until I'm on a roll, through that intersection, or what have you.

It's also no shame (in my shameless opinion) to just decide you don't like clipless if you can afford to be less efficient. I don't ride much with the fast dudes so I can afford the difference... though I am pretty sure if I ever tried it, I wouldn't be able to go back... the pure POWER.... 360 degrees of STROKE... (time to write check to pay bills and remember the virtue of frugality )