Hi Beth!
Welcome back to the Disney Parks Moms panel. It's always great to help out returning Guests. Morning Extra Magic Hours are a great way to squeeze in some of your favorite attractions before the park opens to off site Guests. My family always utilizes these pixie-dusted times in the theme parks whenever we have the chance.
While your husband and older children ride Test Track, a couple of more gentle attractions should be open for you to enjoy with your littlest mouseketeer.
Spaceship Earth is a gentle, educational ride through the past, present and future of communication technology. It also has a few interactive elements during the ride that I know your little one will get a kick out of. Another option for you is
Living with the Land, a boat ride through The Land Pavilion which highlights the future of food production. You'll sail through 4 amazing greenhouses, and even take a trip through a fish farm complete with eels, catfish and alligators. My kids always enjoy this lovely attraction and often ask to experience it more than once.
Kidcot Stations are found in World Showcase which is not open for morning Extra Magic Hours so that would not be an option, but I know you will find plenty to enjoy in the Future World section of Epcot. Please let us know if you have any other questions. We love to help Guests have the most magical time possible on a Disney Parks vacation.
Dream as Dreamers Do,
~Jen