This situation is a tricky one, as your lad could be penalised by his insurance company because someone else was a moron, driving an unworthy vehicle.
Additionally your lads insurance will most likely write off the Freelander, even if it's just a bumper (I've bought many cars in this situation), as insurance companies seldom fix cars if they're over 5 or 6 years old, unless it's something particularly valuable or rare, so your lad could loose his pride and joy, or at least have to negotiate to keep it and repair it.
Me, I'd take the cash (a civil settlement), to avoid the insurance issues, however this moron also needs reporting to the police, as he's broken the law by using an unroadworthy vehicle, and driving it in a manner where he clearly wasn't able to stop, maybe due to speed, to close, drink or drugs, all of which are illegal.
The lad's Freelander.
The damage does look minor, and knowing the Freelander's structure well, I'd say it's mostly cosmetic (bumper, light, etc), however there will be some evidence of the impact hidden under the bumper.
The rear bumper crash member is made of high strength glass fiber reinforce plastic, which holds up well to impacts. The crash member also absorbs and spreads the impact over a large area of the vehicle structure, including the chassis stiffeners.
There will likely be some minor damage to the panels behind the bumper, but I would think the main chassis stiffeners are fine. Normally if the chassis stiffeners have begun to distort, the rear door gap closes, which it looks like it hasn't.
Until the rear bumper is removed, it's difficult to make a proper assessment of what's underneath, but if I was looking for a salvage FL1 to sell on, then I'd buy one with this amount of damage, simply because I've seen what happens in this sort of impact.
Project Tonga I repaired a couple of years ago had similar back end damage, more actually as the bumper was split in several places, but the under structure was hardly damage, and simply needed pushing back out, and a new bumper to return it to it's former glory.
As to whether to take the cash, or go through the insurance, that's up to your lad, but both have pitfalls and benefits, but the other driving definitely needs reporting to the police.