Well, couple of things. Where are they going after they fly down? Best bet is to pattern them and set up an ambush. You'll usually find the toms in a group that big will separate off from the main group (not far away but usually not intermixing) Decoys really won't make much difference because there are plenty of hens around if the toms are interested and calling those big groups usually just gets you a group response back, with no real action. I've never really spring hunted those big groups but have watched them a lot around my cabin this time of year. Unless they are on private ground, chances are also very good that other other hunters have them staked out also. Even though it's only a week away, don't be surprised if they have also broken up by next weekend. When they decide to scatter out, they do it fairly quickly. Guess what I"d do is figure out what field they are using, scout where they are going into it and set up a blind. Be there very, very early though and personally I would'nt recommend calling at them. Just silently wait them out. Dress the kids warm, that last half hour before daylight can be pretty cold this time of year-hard to keep them from moving around when their teeth are chattering.