Just so anyone here knows, there's a surprisingly active fan forum for this series here.
We discuss a lot of different things over there, and it really does say something about these games in that they are so lovingly remembered after all these years.
I've also thought about it a bit, and it'd probably be better if GOG released these games in packs (similar to the Sierra adventure games). Here's one idea of how they could be sold:
Humongous Classics Collection:
Putt-Putt Joins the Parade, Fatty Bear's Birthday Surprise, Putt-Putt Gos to the Moon, and Putt-Putt and Fatty Bear's Activity Pack.
Putt-Putt Saves the Zoo, Travels Through Time, Enters the Race, Joins the Circus, and Pep's Birthday Surprise
Freddi Fish Pack:
Freddi Fish 1-5
Pajama Sam Pack:
No Need to Hide, Thunder and Lightning, You Are What You Eat, and Life's Rough
Spy Fox Pack:
Dry Cereal, Some Assembly Required, and Operation Ozone
Super Duper Arcade Pack 1:
Putt-Putt and Pep's Balloon-O-Rama, Freddi Fish and Luther's Water Worries, Pajama Sam's SockWorks, Spy Fox in Cheese Chase
Super Duper Arcade Pack 2:
Putt-Putt and Pep's Dog on a Stick, Freddi Fish and Luther's Maze Madness, Pajama Sam's Lost and Found, Spy Fox in Hold the Mustard
The two Big Thinkers games and the 3 Junior Field Trips could each have their own pack, and maybe one pack with Backyard Baseball, Backyard Soccer, Backyard Football, and Backyard Basketball together.