Having said that, if I were about to get laid off there are some things that would ease the transition and make it more bearable. First worry is income. If you could guarantee a months severance, that would go a long way. Second is health insurance. If you could have all those resources prefigured out by the time I left, I'd be much happier. Third is promise of future income. If you could have recruiters on standby so that if I could make the choice to begin the job search, it would be great. Lastly, this is sorta extra credit, but experiencing job loss is quite tramatic. You can make counselors / work therapists available to be there in the time of need.
Basically what I'm trying to say, if you are going to let people go, make the only thing they have to worry about is getting over the shock of getting let go. That is unavoidable. But if they know they are being taken care of and empathized with, they'll get over it quickly.