I'm going to have to do some DIY. In and out of the back door is fine and I can obviously lock it. The front has to remain locked at all times. Internal doors are less of a concern but it's a right pain when he (Mij) can pretty much access the whole house whenever he wants.
Eddie can do the lever ones, but it hasn't been a problem so far. I don't think he would try knobs though - very talented Mij!