Do you think I am treating my kittens poorly?

You're not being mean! Unless its like 30 degrees and lower! Even if it is they have each others body heat plus fur. They are super skilled at fending for themselves. Plus, they are outside cats so they have expirence at being outside in the "wild". They will be fine and look at it this way, if they are outside cats they will be happy considering they wouldnt like being cooped up inside! Hope this helps!