Oh, I get that it's a one off in terms of a late night for this tournament. The shared experience with their peers and family (although not in OP's case, as she's said neither her nor DH will stay up) I also understand.
But I still don't think it's a bad point to make that this isn't going to be the last ever WC, it's not the final, it's not so rare that we get this far and it really isn't the seminal moment people are making it out to be. Yes, it's an exciting thing for children to do, but I suspect for some it's the being allowed to be up at that time that will have more appeal than the actual event, not to mention, as OP said, some children being told they can skive off for it in the morning.
I genuinely think parents make more of a big deal out of this than the kids do, to be honest, and if it wasn't being hyped up so much, most kids wouldn't expect to be watching it at that time.
As I said, I think it should be OP's son's choice at 14 to watch it, with the caveat that he still has to get up and got to school at the normal time. But if he doesn't watch it, he won't be the only one and it isn't like he's missed history in the making or anything. And if he does remember for a while that his mum didn't let him watch it, but his dad said he could, so what? I'm sure we all had those times, things we thought were so important, and our parents didn't agree but the naysayer won. I know I have. Why is this any more of a big deal than the concert dad agreed to but mum said no to, or the trip away with a friend, or whatever?