I also have two Power PC-based Macs that run Tiger and therefore have Classic.
But even there - even on an Intel machine, even under Snow Leopard - I can run an older Mac OS, enjoy my older applications, and read and edit my older documents, by using Sheep Shaver.
Sheep Shaver is a Power PC emulator that runs under Mac OS X.
From that point, it was like a normal installation of Mac OS 9.
Within Sheep Shaver’s window, the disk image showed up mounted like a normal hard drive. After that, I applied the Mac OS 9.0.4 update normally.
I recently bought a secondhand 12″ G4 Power Book (more on that another time); it came with Mac OS X 10.4 installed, but I upgraded it to 10.5, thus nuking its Classic Mode capabilities.