Your best bet would be to dig a pit or get some layouts. I would also get some full bodies. If you are going to go with what you got................
If the wind is out of the North, hunt the South end of the field. Make your concealment in the tall grass. If those birds have been hunted at all, they will not go near the trees.
One of your biggest obstacles will be the sound of your calls not coming from the decoys. Set your decoys 50 or 60 yards North of you in the field. Hopefully there will be a lot of wind. When they set up to land on your decoys they should be right over your head. Just remember, if there is any wind at all, the birds will land into the wind. Make sure you have a flag. Good luck.