Hi, Tina!
Welcome back to the Disney Parks Moms Panel!
Although I can’t speak from experience as
Pandora - The World of Avatar is not yet open, I would suggest that if you could only do one, that you experience
Na’vi River Journey as you would be able to experience this slow moving expedition into bioluminescent beauty together as a family.
Avatar Flight of Passage is more of a thrill ride and Guests must be 44in or taller, so you may want to double check your 5-year-old before getting in line or getting a FastPass+. Ultimately, my plan would be to get a FastPass+ for one of the attractions, and then arrive at Theme Park opening to get into the queue for the other. There are also limited “Extra” Extra Magic Hours at Disney’s Animal Kingdom Theme Park that might allow you and your family to extra time to experience both attractions.
Although I don’t really have much more insight for your until I experience them myself, that would be my strategy. I hope this helps you with your planning and you have a magical day!
Jen