unused 529 - best options for cashing out

I live in Florida and purchased a FLorida Prepaid College Plan for my son. He is now 22 and will not be using the plan. I have been hesitant to cash it out because I am not sure how that money will be handled in my taxes. Can you tell me what options I have? I suspect there will be a penalty for withdrawl and possibly it will count as income? But I have already been taxed on it as income and I also can't help that he can't use the plan (due to mental illness). please advise my best approach. Is it possble to roll into a retirement plan for example to avoid penalties? thank you.