Most of these LucasArts graphical adventure games were written using a game engine known as SCUMM (https://en.wikipedia.org/wiki/SCUMM) that was able to target different platforms, which was ported to the Mac and so ran on 68k and later PowerPC Macs. There is now an emulator that can play SCUMM games on almost any platform known as ScummVM (http://scummvm.org/).

Scummvm - http://scummvm.org

Clamshell iBooks are capable of running OSX. Not spectacularly well (they are 366 or 466 MHz machines with limeted RAM), but still.

I don't know how the parent is actually doing it, but many of these classic adventure games date back to a time when there were multiple competing architectures; the games were often written in some kind of bytecode, and getting them running on modern hardware just needs a new implementation of the VM, like ScummVM.

They are mostly pre-intel based games, as Apple switched to Intel in 2002. They are free for download through sites like macintoshgarden.org. Otherwise I use an emulator (Basilisk/SheepShaver) on my own PC/Mac.