If you want to transfer the titles, you can do that through your state's DMV. The kids would list themselves on the policy only and remove themselves from your policy since the cars are no longer under your name.
Like most states, Kentucky requires that any vehicle registered in the state must be insured. In fact, Kentucky maintains a database of all registered vehicles in the state and electronically monitors the insurance status of those vehicles.
You should be able to find a company that would only insure the other vehicle, if that's what you want to do. However, since there is a base cost associated with each policy it's normally recommended that you combine all of your vehicles on one policy since it's usually cheaper.