I'd suggest fast passing Kilimanjaro Safaris and Kali River Rapids.
If he isn't afraid of dinosaurs and the dark, also fastpass Dinosaur. If he is, fastpass Primeval whirl if he can tolerate spinning. If neither ride suits him, then fastpass It's tough to be a bug or finding nemo. I've heard the parade may end May 31st, and I don't know when Festival of the Lion King will reopen, or when fastpasses will be available for that matter.