The tricky aspect about this has to do with the loan and registration. Because the vehicle has a loan in your name, you will most likely be violating your loan contract by not having the insurance policy written for you. Moreover, because the vehicle is registered to you but not insured by you, you're in violation of your state's insurance laws. If you're wanting to pay for the loan and insurance for your son, you would need to have the registration transferred to him as well as the loan contract and simply make payments in your name. This would be dependent on the individual stipulations of the loan, of course. You can transfer registration to your son via your state DMV's department.
I recommend looking at the loan policy as well as contacting your state's DMV department. Best of luck!