You will want to get them used to being outside. You might put them out in a tank or container outside for a while the days before you move them. If you're not going to watch them, be sure it's predator-proof. It would be better to watch them. Just to get used to the temperatures, you could simply open the windows in the room with the turtles the days before moving them. It may be easier for the new person who is taking them to acclimate them to the new temperature. Luckily, they should adapt to new water quality much easier than fish. I assume the pond they are going to is fenced? If not, the turtles will walk away. If the pond is deep enough, they can overwinter outside but it's safer to bring them in. If left outside, they would lay on the bottom for a few months like the fish, just waiting. The pond would have to have an opening in the ice and some sort of aeration in place so the turtles wouldn't suffocate under the ice.
My page on turtle ponds is at
http://www.fishpondinfo.com/turtles/turpond.htmGood luck!