I'd say get the T|T3. Since they're both out of production, it shouldn't cost that much more to get a T3 over the T2. I've never used a T2 before, but I have used a T3 for almost 2 years now.
Some clear pros of the T3 over the T2:
-uses a virtual Graffiti area. You can hide this when using many Palm OS apps (that came with the handheld) to get a larger viewing area. Some 3rd party apps will also support hding the Graffiti are for full display. Not alot, but the bigger/more popular 3rd party apps will support this
-you can recustomize the Graffiti area shortcuts
-when u bring up the virtual keyboard, unlike Palm PDAs with solid Graffiti areas, the keybaord replaces the Graffiti area instead of taking up more screen space at top
-I hear the T3 is actually usable when the slider is closed since there's a status bar that you wn't find on the T|T2. The statusbar gives you quick access to the usual stuff you'll find on the Graffiti area like home/applications launcher button, find button, and options/menu.
You'll also find additional buttons for quick access, like bluetooth, write anywhere toggle, rotate/pivot screen (landscape/portrait mode), and hide/reveal Graffiti area. The clock tells the time, but u can tap on that to get the date, battery info, and memory usage.
Just keep in mind a T3 can go up to $300. I suppose you could chalk it up to it being a learning tool to your parents, even tho one could load a bunch of games and emulators on there, since that's about how much a PSP goes for these days.