Since the panel description on the Chicon website reads "J.R.R. Tolkien
and C.S. Lewis are the best known of the group, but there were other
Inklings too," it seems to me that what you're really on is a Charles
Williams panel. He's the real "other" Inkling, and the only other one
who wrote fantasy, so he's the one you should focus on. And it so
happens that since our book of Williams has actually been published, I'll
bring a copy along and you can show it off on the panel.
Sayers can also be mentioned, but she was a Friend Of, not an Inkling.
The other Inklings most worth mentioning, to an audience which doesn't
want the boring scholarly blither that I'd probably contribute if I were
a panelist, are:
W.H. Lewis - CSL's brother, author of some delightful volumes on French
history of the Louis XIV period (especially _The Splendid Century_) and a
superb diarist: selections of his diaries have been published under the
title _Brothers and Friends_, and are a good picture of CSL as well as
interesting in their own right.
Nevill Coghill - a literature professor at Oxford, he specialized in
drama and directed some notable Shakespeare productions, as well as
Richard Burton's film of Marlowe's _Doctor Faustus_; but to a literary
audience he should be most noted for his fine translation of Chaucer's
_Canterbury Tales_, in the Penguin edition.
Owen Barfield - somebody other than me will have to try to boil him into
a paragraph, but essentially he was a philosopher of language whose
thought deeply influenced both Lewis and Tolkien and enriched their
work. The Barfield books to start with are _Poetic Diction_ and _Saving
the Appearances_: the latter in particular will be appreciated by anybody
who was interested by Julian Jaynes's _The Origin of Consciousness in the
Breakdown of the Bicameral Mind_. Barfield's influence on Tolkien is
well described in _A Question of Time_ by Verlyn Flieger.