Hey rem700phil222,
Using apple juice would be fine, but I would suggest that instead of simply using apple juice as a brine, you should consider injecting the turkeys with some form of a soluble seasoning.
By injecting with a soluble seasoning, you will retain more moisture than by just simply brining the turkeys. Many soluble seasonings also contain sodium phosphate. Sodium Phosphate helps in retaining moisture because it binds moisture in the product, resulting in a juicier, moister and more tender product.
We sell a variety of soluble seasonings, one in particular, that I would highly recommend, that is specifically formulated for injecting turkeys.
Click here to view a variety of soluble seasonings (the soluble turkey seasoning is the 5th item on the page)
As for a cook/smoke cycle, you can smoke it in a variety of manners. According to FSIS and the USDA (known as Appendix A,
click here for link), the danger zone is: "Dwell times of greater than 6 hours in the 50°F to 130°F range should be viewed as especially hazardous", so its a little bit different than the 40-140 mentioned. Just be sure to hit the right internal temp for poultry of 165-170 degrees to be sure it is cooked and has reached lethality. Also, remember that there is also a danger zone for cool down cycles. According to FSIS and the USDA (known as Appendix B,
click here for link) "During cooling, the product's maximum internal temperature should not remain between 130°F and 80°F for more than 1.5 hours nor between 80°F and 40°F for more than 5 hours." The 'rules' do change for cured products, but I am guessing from the sound of things that you are not planning on using cure or sodium nitrite.
Good luck with the turkeys, and I hope they turn out great!!!