Staying on site in June, planing be to do EE at AK 8-12, hop to HS for FPP+ reservations until 4 then back to AK for Rivers Of Light that evening. Is this doable?
I would say absolutely! Especially if it’s true that ROL will have several performances a night, if you find you’re running late at HS you have the option of choosing a later show at AK.
Absolutely doable - lots of people do 4 parks in one day so the equivalent of 3 should be fine. You will have a blast.