If they're closer to 7 days old, vs 13 days old, the warm area should be closer to 85-90F. But you can also go by their behavior: if they spend a lot of time clustered under the heat, they're too cold, and if they spend most of their time as far from it as possible, it's too hot.
I don't do a...
They don't need stuffed animals. They need appropriate feed and water, a warm area to warm up in, a cool area at least 10-20F cooler to cool off in, and plenty of space to be able to move around otherwise. As long as you meet those basics they'll do just fine.