Okay, why do you want the turkeys dead is the first question. Because if you want them for the meat considering the holidays are coming, the last thing you'd want to do is poison them to get it. Makes no sense. If meat is the answer, why get them, spend all the money on food, fencing, and housing just to end up with meat I sure wouldn't put into my family? What that turkey inhales goes into the blood stream. The blood is what feeds the cells, and the cells make up the meat. Here we have half the world up in arms about not feeding Non-GMO and only wanting to raise birds on organic and/or gluten free food and maybe 30 pounds of meat being poisoned.
If you want them gone because you just don't want them anymore, save yourself a whole lot of money and take them to the nearest shelter and ask them to do it. It might cost you some money, but you owe it to those birds to treat their last day with at least a modicum of dignity and a painless end. It will cost you less than all the plans you currently have. Put an ad in the paper or Craigslist - surely this time of year someone will take them and kill them as it should be done, quickly, safely, and utilizing the gift of the meat for their families.
I'm trying to understand, I truly am. But I'm dumbfounded and I admit it. If you took on the turkeys, then you are responsible for them from the time they come into your possession until the time time they leave, and that means you have to have the courage to do the right thing. Sticking them in a plastic playhouse full of poison just ain't it.
Now I'm going go back into my corner and watch this unfold because sadly I can't do anything about it.