Richard,
Thanks for your question to planDisney!
While each of the Disney theme parks have great backstage tours, my family is most excited about the ones at Disney's Animal Kingdom Theme Park. I have a daughter who volunteers at the local zoo and at a veterinarian's office, so she is officially in charge of deciding which tour we do next!
You will find that the Animal Kingdom park tours offer a close-up way to see the amazing animals in their care. They are all guide-led, so you get a knowledgeable cast member that enhances the experience with information and in-depth knowledge of their care. Some of these tours are just now returning to availability, so you should have several to choose from. The ones that I think hit the highest marks include these
Wild Africa Trek - This is the best known of all the Animal Kingdom tours. The 3-hour guided tour includes a scenic lunch overlooking the savannah, a rope bridge walk over the crocodile enclosure, and more animal experiences than I can list here.
Up Close with Rhinos - A shorter experience that has a duration of about an hour, it is both informative and engaging, but also fits more easily into a day where you might want to get more park time in. They also just had a new baby rhino birth, so you might get to see Mylo in person.
Caring for Giants - Elephants are the stars here, and like with the rhino experience you get a guided experience that clocks in at about an hour.
At the time of this answer all three are listed on the website as currently unavailable. But don't worry, Disney has already announced that they are returning these to availability in early February 2022. In the next few days you should be able to book them for your magical escape.
BONUS TIP
The cost of these tours does not include your park admission, so make sure you have a Theme Park Reservation for the Animal Kingdom that day, and a park ticket.
Write us back if you have any other questions.
Have a Magical Vacation!
Doug