If you are just going to do file and printer sharing, doing it in Windows is much easier than on Linux. However, you might be able to set up a Windows Domain using Linux (which you cannot do, as far as I know, on Windows XP- you'd need Windows Server, meaning $$$). The advantages of a Windows Domain on a 3-machine network are, on a practical level, probably not worth it, but the tinkering would be interesting.
edit: That of course if your laptops are running XP Pro. If they are running XP Home they won't be able to join a domain.
As for the things you can do on a Linux box, that mostly depends on your interests.
I you have system administration inclinations, I would definitely recommend you to install Linux, learn to set up Samba for the filesharing/printsharing, remote administration via SSH, etc.; basic Linux administration skills are interesting even for Windows-focused admins. You can add more daemons you might want to learn to admin, such as a web server (Apache's httpd), mail server (Postfix for SMTP, Dovecot for IMAP), db server (PostgreSQL), etc.
On a higher level, there are tons of apps which run pretty well on Apache+PHP+MySQL which you might want to know how to install and admin, such as, for instance, Mediawiki, Wordpress, etc.
If you are more development-bent, you might want to learn how to set up a server for your apps and deploy something to it, such as a PHP app, Java app, etc. This is interesting, as it's fairly cheap to rent a Linux virtual server, and having one at home is excellent for getting acquainted. Then you can deploy apps you develop on the shared server so that they run in a "pro" environment (network redundancy, UPS, etc.).
You can also run anything you want to leave running 24/7, such as downloads, or want to have available from everywhere (people still run IRC clients on Linux boxes so that they can access them from everywhere, for instance).