At DHS:
For the 8 year old: Star Tours, Meet Chewbacca & Kylo Ren at the Launch Bay, March of the First Order Show with Captain Phasma, Toy Story Mania, Rock n/Roller Coaster, Indiana Jones Show
For the 5 year old: Star Tours, Toy Story Mania, Rock n'Roller Coaster if she's really tall!, Ariel show is fairly lame here, but see it anyway if she loves Ariel
At MK:
8 year old: Hall of Presidents, Space Mountain, Big Thunder Mountain, Splash Mountain, Buzz Lightyear
5 year old: Journey of the Little Mermaid, Meet Ariel with her tail, Meet Minnie & Daisy in Circus costumes, Mine Train, Space, Thunder & Splash if she's tall enough, Buzz Lightyear
At Epcot:
8 year old: Soarin', Test Track, Spaceship Earth, each of the countries for the history, Mission Space
5 year old: Soarin', Test Track
At DAK:
8 year old: Everest, Safari Ride, Festival of the Lion King Show (best show at Disney IMHO), Kali River Rapids
5 year old: Everest if tall enough, seeing the gorillas (my daughter loves them!), Safari Ride, Meet Minnie & Mickey in safari costumes, Lion King Show, Kali River Rapids