Welcome to planDisney Jasmine!
Please read through the
list of Prohibited Items on a Disney Cruise. It specifically lists diffusers, so I am not sure if a battery powered one would make any difference.
The list does say that humidifiers, if approved by the Chief Electrician, will be permitted. You are welcome to bring your humidifier that uses oils. If it is not approved, you will be able to retrieve it after you leave the ship on debarkation day.
I am sorry I do not have a definite answer, as the final call on this would be with security and the onboard electrician. Everything is done keeping safety in mind, so please understand how these decisions are made.
We have chatted about what NOT to bring, let's get to the good stuff of
what to pack! Start with your swimsuit, sunscreen, sunglasses, hat, a tote bag for
Port Adventures, cruise casual clothing, and a sweater for cooler evenings. Your stateroom will have a hair dryer, shampoo, conditioner, body wash, and plenty of towels so no need to fill up your suitcase with those items.
WISHing you a MAGICal cruise where DREAMs come true!
Cathy