Pay half of little dent?

In a restraunt parking, I looked back, saw no one, so I started to back my van up. Then I felt the bump. I said, “What could that be?” I bumped a small car. It was so close I could not see it when I looked back. So there is a small bubble in the bumper and the paint in that area is cracked.
To my suprise the guy pulled a auto body shop card out of his wallet. He said the shop was his friends. We agreed to get 3 estimates to choose one and have it fixed.
I came to find out this guy works at the body shop. I went there and got an estimate. The shop owner is offering me a discount because, “Juan is being paid to work on his own car.” (By-the-way, Juan was not happy that I found out that he worked there.)
The price he gave is $300.
I want to offer Juan $150 to have his car repaired. I feel he has some fault in this for being so close behind my car. Am I wrong to want to pay half?
I meant “restaurant”

you can try but if he does not accept pay the hole thing
because ir he deciedes to file a police report and call your insurance you will have higher cost and pay the hole thing

Auto Repair Eating the Cost of Installer Errors