@FullMoomin
As others have said, the money was there to spend on them.
The long term effects of growing up with the benefit of this money will outweigh being handed 20k at 18 (if that meant growing up in financial insecurity).
So relax. Easier said than done, I know. I usually need a plan or remedy to move on from when I feel I've made some sort of mistake...
I have seen a lot of parents hand over around 20k when their kids reached 18. In my experience it's too much too young. I've watched it wasted on failed attempts at FE, new cars bought that immediately depreciate (cars are a terrible way to spend a lump sum that may never be repeated), once in a lifetime trips to celebrate turning 18. Totally wasteful and transient things...
If your child can be supported through FE through family support and getting their own job/student loans etc, then 25 is a much better age to have a windfall. If they aren't going into FE it may also be better to work through those first demands of the transition to adult life without the ease of throwing 20k at those first steps. It's the age of biological maturity rather than the accepted 18. It's a time when deposits for homes are a higher priority, or starting a business. Something where the money will be an investment into lasting security.
So, if you have the means (and I appreciate that beyond 18, the CB won't be there) could you start saving for them, with the goal of handing over at 25 and get an extra 7 years? Share account details with family who might add the odd fiver, it all adds up. With all savings it's about consistency over time, even with small amounts, and the cumulative benefits.
Note of caution: certain accounts have to be handed over to children when they turn 18, so to do this, you either need to trust that your kids agree to your plan or put it in your own name, or look at other means of having it in trust.