Nothing is safe. All life is about risk and mitigating that risk and people are terrible at measuring risk. The risk of abuse in a
DCL kids club is almost infinitely less than a scout troop, school, or other youth group. There are very strict protocols in the kids clubs and they're enforced by the personnel infrastructure. There's full video surveillance to confirm anything. And while they may not have prevented this from happening, having two CMs in the room almost certainly limited its impact, and allowed a quick confirmation that the line acted on rather than trying to cover it up.
Math: The US has a traffic death rate of 12.4/100,000 population. That means for every 100,000 people, 12.4 will die in a given year from an auto accident. Disney carries several hundred thousand guests a year probably a third to a half of which are kids. And we have two instances of abuse in the line's history. Assuming you cruise once or twice a year, you have a better chance of your child dying in a car accident than being abused on a DCL cruise.