I would never take a baby that young at any time of the year, but during cold/flu season, and with this year being a particularly busy one, absolutely not! This is the worst time of year to go due to busy crowds, cold weather people bringing viruses to WDW, and H1N1.
I really get tired of reading people say that people shoudn't keep their newborns inside as it won't build immunity. Good docs will tell you the opposite - they need to be protected at that age as little things like colds/flu, can and do turn deadly. You should not be bringing them into airplanes, crowded shopping malls, etc. at that age. If there is an emergency, then that may be a different story (eg. flying to a funeral). Our ped and family doc say that little things help to build immunity and are important, but taking a newborn to one of the most crowded places on earth, is not the answer, as there will be major serious things floating around, and those things can be very dangerous for newborns. Those won't build immunity, but in fact, harm their immunity. BTDT with babes with pneumonia in the hospital, and it takes a serious toll on their immune systems, as well as takes months for their immune systems to get back to normal.
I wish the OP good luck in his/her decision and a healthy trip if he/she goes, Tiger