I like how everyone here has an opinion on what OP has to do in his life, and how he should not date a woman whose mother thinks like that yada yada instead of helping the man with the actual thing he asked
OP, 12 cm is possible bro. But it is high risk, you will need to lengthen both segments, it will be very expensive, and it will take a long time to recover (possibly 2+ years and that's in a perfect world), and probably forget any athletic ability
From what I understand to you height is more important than any of this. The answer is yes you can lengthen 12cm.
As for your children ending up short, well, that is not guaranteed to begin with,usually children of short parents tend to be taller than them even if they are still below average, that is the regression effect, and, at the end of the day, if we are going to be so cynical, if your child ends up short, you will be the guinea pig to know if this is safe for your child. That's how I think about myself at least