Turtles and outside temps

So apparently I've become the person that people give their unwanted turtles to. I don't mind all that much...I like turtles:) Here is my question:
I've put together a stock tank pond for the Slider and the Pinnensula Cooter. I'm wondering at what water temperature they can go in the tank? It's an above ground pond that is about 120 gallons.
Also, I have an African Sideneck. Can he go outside in the summer too? I live in Minnesota so I'm pretty sure outdoors in the winter is out of the question, but that's ok. I just don't want to shock his system when they go from room temperature water in the house to the outdoor tank/pond.

Interesting.

My guess to put them outside would be when the pond water matches the water you keep your inside tank water temperature. Depending on your tank temp, you could feasibly drop the water temp slowly to match outside water temp when you want to put them outside. So if your indoor water temp is 75 and the outdoor pond temp is 70, drop the indoor water temp 1-2 degrees per week(?) over the course of 5 weeks. Then you could put them outside? Or wait until the outside temp matches your indoor temp.

The sideneck I would guess putting him outside around 75-82. I had a sideneck and still have a west african mud turtle. Aside from diet their care has been similar to RES in terms of water and basking temps. Though the sideneck was more prone to basking multiple times a day for 15+ minutes while the mud turtle doesn't seem to care for basking for more than 15-30 minutes 1-2 times daily.

I've been doing some turtle watching around the lake at my nature center. The red bellies, painteds, and snappers which have been actively basking and mating the last few weeks at least with air temperatures ranging from low 60s-low 70s during the day while the waters are warming up, which are probably in the low 60s(estimated, I should take a therm with me and verify). Almost like air temp doesn't matter as much as a nice sunny basking spot does.