I think the problem here is with xfce, we have the same issue. I am the only geek in the house, wife and daughter just want the computer to 'work'. In xfce the action plugin has the switch user option greyed out, the others are all available, restart, logout etc.
We actually run KDE because we can log everyone in and switch user with a couple of clicks. Sure there are the ctrl-alt-F* options and I'm quite happy with that but they're not and I can see why. To them the computer is just the screen in the corner where they look at ebay and play games.
I think xfce needs a switch user option, whether the developers think they do is another matter.