I understand. I sleep under a ceiling fan all year long, and miss the soft whirrr when cruising. I don't take a fan simply because I don't want to lose my valuable luggage space. I can do without most anything for a few days...but yes, I do miss my little night noise and breeze.
I don't believe there would be any problem with your taking your small fan. It would use less power than some other appliances people take on board. (My desk fan is only about 6"x5", but still too bulky...to me.) However, if you feel you have the space, go for it.