Hi Steve, sorry to hear about the accident and hope your dear wife is ok and hasn't got any issues like neck pain (sometimes appear later on!)
It's a very risky situation with insurance in this position. I believe you are required to tell them either way. This also leads to your premium going up even though your not at fault, you just being in this situation means they will increase your premium, I know its really wrong but they work like that.
If this guy decides to throw a wobbler later on, and refuses to pay, then what will you tell the insurance? they will ask why wasn't it reported? this will also go against you.
I'd agree with guy he pay for an inspection with the rear bumper removal costs paid by him, and carried out asap, with the premise that if there is body damage, you will go through insurance.
I suspect you will likely have some damage to the area behind the bar mounts, therefore more damage than you may think.
Sarge