I would put that thing in the smoker Saturday evening. On Sunday, depending on how early it's done, double-wrap in foil and keep warm at 140 in your smoker for several hours and rest for 2 hours, or remove and reaheat if it's way early. It seems like every time you do a brisket or butt for company, it's never done early enough. Error on the side of being done early. Brisket holds well. As far as the water pan, it really doesn't matter much if you use apple juice or water. It won't impart much flavor during smoking. I just use apple juice, and save it from the water pan, since it sometimes comes in handy as a flavorful liquid to add for reheating, or to add to portions when freezing.