In light of this comment, I'd like to offer this. Note that my suggestion to use Windows still stands, but if you really want to use Linux here are my suggestions:
I used to use Edmonton FreeNet for my internet access. Now, this will be a bit of a tangent at first, but bear with me. The thing with FreeNet was that everything was really simple. You dialed in, got a Unix (AIX, IIRC) login prompt, entered your user id and password. Instead of a shell, you got Lynx showing you a menu plus various instructions and news about the system. From here you could use the links to access email (pine), usenet (tin), the Lynx file-management tools for your home directory, or the rest of the web (the 'g' command).
FreeNet was a really nice and easy to use system that was used by many people. Based on the postings in the local freenet.help newsgroup, the users in general were very computer savvy, but even the not very computer savvy users had little trouble with the system once they got going.
What am I leading to? The idea behind it all.
The idea was to make it as absolutely simple as possible while not dumbing it down to the point of non-functionality. This is best reflected in their choice of mail client, Pine. Pine is a "nice" email client that is easy to use, has extensive online help, and in their default configuration it works very well for most people. This is, in my opinion, the major goal you should have for this setup.
How does this apply to you?
You should strive to make it as simple as possible. Don't give them Gnome or KDE, they probably don't really need it. Don't give them something like twm either, unless you want to customize it. You could give them WindowMaker with dock icons to launch a web browser, email client, word processor, etc. You would have to customize the WindowMaker root menu a bit to remove a lot of the stuff they won't use. As an alternative to WindowMaker, you could try fvwm95 if they are familiar with Windows. It will shorten the learning curve a bit.
For an email client, I'd suggest Pine in an xterm. Seriously. In an xterm, Pine can have mouse support so that they can still point and click to their heart's content, plus it really isn't all that bad of a program once you configure it to your liking. It can be configured to open URLs in the web browser of your choice, which could be a good thing.
If you really, truly want a graphical email client, I'd suggest avoiding anything complex. You don't need an email/calendar/task list/journal/whatever like MS Outlook, you need an email or email/news client like Outlook Express. I know we're talking about Unix programs, I'm only using those as examples of the kind of functionality you should aim for. For a concrete suggestion, I'll throw tkrat into the mix. I used this for a while - it was really nice, but kind of quirky.
For a web browser, I'd suggest an old version of Netscape. The old ones are usually more stable. You could also go for Mozilla, but I think that is overkill. If you use WindowMaker, they will be able to click the dock icon as much as they want but it will only launch one copy of it. FreeBSD uses something called netscape-wrapper to make the launching of Netscape a lot saner (ie, if you have Netscape open and run 'netscape http://blah/' it will open a new window instead of a warning dialog), you may wish to consider using this program in conjunction with Netscape.
If you want a newsreader, I can honestly say I haven't found one for X that I like. Pan looks good, so does Knews, but I use slrn in an xterm.
If you want ICQ for them, I have to recommend Licq. This is the best ICQ client I've found for Unix.
For a word processor, well, that gets tough. My initial impression of StarOffice is that it is too quirky, complex, and just plain weird. I didn't like it. For my word processing needs, I still use Word on a Windows machine. WordPerfect for Linux looks ok but doesn't seem nearly as nice as Word for Windows. Beyond that, I have no experience in this area. You could try getting an old version of Word (say Word 6.0 or Word 95) to run under Wine. I think this is pretty sick, but it might be the best solution. I really don't know what the state of the various word processors for Unix is though, so I can't offer anything more concrete.
Someone else suggested that there is a lot of stuff that comes standard with Linux that you probably don't need. The example I remember seeing was SSH. I would recommend leaving this in just so that if anything breaks you can fix it without having to leave your place. If you make this into a distribution, you should definately have this for whoever will be maintaining the system.
Now that this has almost become a complete article in its own right, enjoy! Hope that helps.