I would not see any problem with using the VPN client on there computers because they have xDSL as there transport. I would however from a management and security aspect not want to attach all of them to my PIX. Not to say it could not be done depending on the PIX and your internet connection to it. You can use preshared keys. I would however look at using a VPN concentrator and strong authentication as the management time and security holes associated in doing it this way may be considered poor by some. Not to say I have not done it that way in the past, but new tools and PKI have made it much easier to set up and manage as well as secure.
