Good luck with your EFs! Hope you'll post photos in the spring. They'll love free ranging and their screeches will make it sound like you live millions of years ago when dinosaurs roamed the earth. If you have close neighbors, be sure to drop off some earplugs and fresh eggs to keep their good will lol.
@microchick is breeding EFs with other resistant breeds to raise Mareks resistant chickens with success. I also think that with good biosecurity, etc., you may never develop Mareks in your flock. Mareks came to our flock through an unethical local breeder who knowingly sold infected chicks.