Intentionally creating people less happy than I am

This probably isn't the same as "creating people with lives worse than the current average".

your personal happiness level being the baseline

Why would that be the baseline? I'm lucky enough to have a high happiness set point, but that doesn't mean I think everyone else has lives that are not worth living.

Would you want to bring unhappy children into the world?

Unhappy as in net negative for their life? No. Unhappy as in "less happy than average"? Depends what the average is, but quite possibly.