Are we gonna be at fault for this car accident because of my son's age?

My son has had his license for a couple of weeks. He's almost 17 and I decided to let him drive to Starbucks. It was close by and I would be in the car with him. I'll admit was son was going a little slow. The speed limit was 40 and he started off going 25 and I told him he could go a little faster so he was between 30 and 35. When we got a Starbucks he was still going a little slow and when the light turned yellow he did slow down even though he could have made it had he sped up. Another car sped up and rear ended us. We got out the car and couple started screaming at us asking why we didn't go. They were yelling at my son and I told them to talk to me not him. I'm his mother and they said he shouldn't be driving. My son started having a panic attack and I sent him to sit in the car. They demanded to see his driver license and I said I would give it to the police. They claimed our car had no damage even though it did. They were yelling that my son is stupid and when a light turns yellow and you're that close you go. The police came and took down both our statements. He did tell us that they will most likely be at fault because end of the day they rear ended up but the wife started screaming wait until the insurance sees his age. She said that multiple times. I have told my son maybe he's too nervous to drive right now and took the car keys away for the time being but will we be held responsible because of his age?