Sorry, but even (and especially) if you believe it really happened, the slaughter of Egypt's first-born is just horrible and not a fit subject for a children's cartoon.
The only lesson I can see being taught here is that it's okay for your enemy's innocent children to be killed so long as it benefits you and your own nation/people.
AIBU to think that there is no way this would have been deemed acceptable to be included in a children's cartoon if it weren't a biblical story?