I did this for the first time last year. Came out great, but I made one mistake.... When doing the ice bag on the breast, make sure you pull the turkey out of the fridge and let it warm up on the counter slightly before putting the ice bag on.
I pulled the turkey out and slapped the ice bags on right away and did not get enough temperature variation between the breasts and the rest of the bird. I think you want about a 20 degree difference, so if your ice and breast is close to 34 degrees, the rest of the bird should be higher before you put the bag on to get that separation.