I hear ya Jim,
When one is unable to do so they should never feel bad. I am sure they do not expect anything, and if they do, they do not deserve it anyways LOL ... and hey - you keep them in those nice cars so they should feel blessed by you already

I think it is a nice gesture when one wants to, but definitely not an obligation in any way. ... and hey, a nice thought written in a christmas card goes a long way to brighten their day when you wish to express gratitude to those special ones along the way.