Irrespective of the damage to the car, I’d cancel the holiday. It’s far too expensive to risk it being a nightmare. It sounds like it’s more suited to childfree holidays anyway.
IF I felt like going away still, I’d book something with far less pressure attached, or arrange for all of the children to be looked after and go away with DH for a couple of nights.
As for the car...I’d be furious, and he would know it. He would not be sulking about having to pay for it, because that would be the least of his worries. He’d be losing any and all gadgets, treats, freedom out with friends and anything else I could think of until he started actually being sorry for his actions, instead of for needing to pay for it. I would tell him that if he had anything he wanted to talk about, I was there for him, but that doesn’t excuse his wilful, destructive behaviour. Being soft on a thirteen year old because they have a sibling on the way is NOT a good idea. It just teaches them to make excuses for their shitty behaviour. Teach him to TALK, not act out, IF there’s an actual problem. That will stand him FAR better in the future than making excuses for him.
God knows whether the new baby is bothering him or not, but he needs teaching that you TALK about what’s bothering you, you don’t destroy things and act like a complete little shit in general. If more parents taught their kids this, there’d be far fewer entitled wankers in the world cheating on their partners, treating them like crap and generally thinking the world owes them.
You say you love him, get those boundaries firmed up.