Sorry to hear that you lost your son. I don't believe the parents of the 17 year old have a valid claim against you as a parent. From the description you provided it appears that the vehicle was titled in either his name or the prior owners name. If the vehicle was not titled in your name then I don't see where you would be liable. If the vehicle was titled in your name then you would be liable under Florida's Dangerous Instrumentality doctrine and not because he is your son.