Another choice might be Wayne and Shuster: the radio years: the best of the best which includes the memorable Rinse the Blood of My Toga featuring that famous line, "I told him Julie, don't go" or the full cast productions of Agatha Christie mysteries.
A road trip with children might be a great time to enjoy together some children's books like Holes by Louis Sachar, A Wrinkle in Time by Madeleine L'Engle or the Harry Potter books, or maybe a good time to introduce them to some classics like P.G. Wodehouse or The Hitchhiker's Guide to the Galaxy by Douglas Adams.
Perhaps you have some favourite audiobook choices you would add to this list:
Life With Pi by Yann Martel
Jonathan Strange and Mr. Norrell by Susanna Clarke
The Amazing Adventures of Kavalier and Clay by Michael Chabon
All Things Bright and Beautiful by James Herriot
The Curious Incident of the Dog in the Nighttime by Mark Haddon
A Short History of Nearly Everything by Bill Bryson
The No.1 Ladies Detective Agency by Alexander McCall Smith
Minding Frankie by Maeve Binchy
The Graveyard Book by Neil Gaiman