Here are two more options:
1. Find a cheap old Mac that is in good shape and can run a version of OS X that supports PowerPC programs, then keep the machine around for exactly that purpose. I have a Black MacBook I keep handy for this running Snow Leopard.
2. If the CD-ROMs are 90s vintage (I have a few of these, mostly musical interactive CD-ROMs from Bowie, Laurie Anderson etc), you'll need to find a good used machine that can run OS 9 or Classic in OS X. I have a 14" iBook for this purpose.
Oh wait, just remembered a third option:
3. If you've got the time and skill and resources, you could try making
Sheepshaver work on your current machine. Sheepshaver can emulate OS 9 or OS 8 (or earlier if needed) and still works in Mountain Lion but man oh man is it a ... um, witch ... to set up!!