Several years ago, my mother got herself a computer. I lived abroad, so she did that all by herself. When I came back, I fell into the trap of doing computer maintenance for family, and finally I got tired and told my mom I'd install Mandrake on her machine. She said okay as long as it worked like Windows. Sure I said, you'll see...
So I went buy a mandrake CD, installed it, gave a small course on how to do things on the machine, and told her how she didn't have to worry about viruses and spyware anymore, etc... The first thing she said to me was : "but my CD with the program to remove red eyes from photos doesn't work on it. And neither does my cliparts utility, and the fun online postcard programs my friends sent me by email." and I thought, shit, I didn't think about that. So I tried to get her to use Gimp and other open-source utilities, but it wasn't "the same", it wasn't "her programs".
So eventually I told her, look, it's either Linux with no worries, or Windows with all your toys, but you worry about security and backups yourself. She chose Windows, never once called me for support anymore, and that was it.
My mom is 70 and now owns 3 computers, including an EeePC that she keeps in her purse all the time. So the moral of that story is, unless your "senior citizens" (also called old persons in non-politically-correct circles incidentally) is mentally deficient or just not interested enough, don't take them for idiots and tell them that, yes, computers are a pain, and you've never had one, and yeah it'll be a tough learning curve, but you're perfectly able to do it. And don't let them use their age as an excuse for laziness.