Damaged a parked car while parking; now on the hook for $$$

[matt]

My teenage son was backing up to parallel park but was too close to the parked car he was trying to park behind. Unfortunately our 2 month old car scraped the rear panel / bumper of the fairly new Nissan Rogue before I could tell him to stop. We did the right thing and left our phone#. The owners were of course grateful we 'fessed up instead of driving off. So now they've sent along a repair estimate for about $1,400 from a body shop through their local Nissan dealer. Based on my own recent experience with some body work and related painting, the cost doesn't seem way way out of line. But what suggestions would anyone offer for my response. I want to be fair and know it's already a hassle for them but if I can payout less, that would be even better. Can I direct them to get another estimate through someone of my choosing?