Hi,
Having been through this on a personal level with a Limited company, I inherited the family business when the old boy passed away, it is very easy to sign over a business under these circumstances. Your accountant will file all the papers. It will definately be easier if your son is working for you at the time but your accountant will guide him in the right direction.
Also on a big note he has to be careful when it comes to the business finances ie overdrafts or loans as I found out the hard way! usually all loans will have been personally guaranteed, he will have to sign to swap over the bank accounts so he needs to read everything carefully and make sure he doesnt shoot himself in the foot as I did. I signed the personal guarantee not knowing what I was signing at the time and it came back to bite me later.
I would suggest that should the unfortunate happen and the business owes money then just shut it down, all bar the phones etc and re-start. All of your customers will understand, HINDSIGHT........ a wonderful thing!
Matt