Include Emacs, of course, but you might want to have something gentler.
The Lisp environment I found easiest to slip into was Macintosh Common Lisp, with the FRED editor (Fred Resembles Emacs Deliberately). Digitool didn't successfully make it into the current era of Macs, but they open-sourced a lot of their stuff as they folded. Try www.clozure.com or search for "openmcl" on Google.
There was a project to get the Fred environment running on Openmcl, but I don't know the status offhand (I haven't done anything with Lisp in a long time, and haven't been paying attention on the mailing lists).
So, my recommendations:
Ask Paul Graham if you can include "On Lisp". Since he's giving away a download for free, the odds are good that he'll give permission. (His other excellent Lisp book, "ANSI Common Lisp", is apparently still selling, so it's unlikely he'll give you permission there.)
At least check out the MCL stuff to see if there's anything you can find to make it easier. Emacs is a great Lisp environment, but it's a bit intimidating for the beginner.
I haven't looked at the SBCL documentation lately. Is it fairly readable and beginner-friendly? Perhaps somebody could write up some quick instructions on how to get going and how to debug. Emphasize mouse use at first, even if using Emacs.