Can't you get someone else to take them as a birthday treat? When he was about 10 my son really wanted to go to Thorpe Park (some friends of his had already been) and so we said he could go for his birthday. I said he could also invite his TWO (note TWO) best friends, George and Josh, along as well. But he had some other friends he wanted to invite, plus he owed some return invites from other parties. We kept increasing the number until we ended up taking eight! I had to hire a bloody minibus.One of the great advantages of not driving is that I have a ready-made excuse to avoid going to Alton Towers - it's a place that's completely inaccessible by public transport, so the kids have no chance.
I was staggered to see the prices though; I think our kids would have no chance of going there even if I could drive.