You might have a problem with finding an outlet...there are now outlets near the nightstands on the Dream and Fantasy, but for me, that would be too much scent right where I'm sleeping. I think the only other outlet is near the desk, and if you're like most people, that's where you'll want to charge your camera, or plug in a curling iron or some such.
I know that in the past, when we've cruised at Christmastime, the stateroom hosts were instructed to remove any decorations that were plugged in, so you may have a problem with that, too.
I take Gold Canyon's hanging car air fresheners. They're easy to pack, wrapped in plastic, and you remove a small portion of the plastic as each day or so goes by.