It will be interesting to see if the babies grow up with any side affects from the editing. DNA is hugely complex and changing some elements of it could easily effect other parts (I imagine).
Statistically cas9 is barely worse than just be born to a late parent.
Depends on what's being mutated. It seems likely that 1. random mutations with catastrophic outcome would be negatively selected for evolutionary, 2. Humans try to meddle with genes that may be disproportionately important.
So I'd put the risk of gene editing quite a bit higher.