So if the only known family member is jailed for a 30 day sentence, do we send the child to jail? Or do we separate the child from the family?
I doubt you'll get an answer.
Even though it is a misdemeanor, you can't release them because they would be guilty of committing the same crime immediately after being released. If you get arrested for being drunk in public, they detain you until you are sober(legal). They detain these illegal aliens until they become legal. There is no point releasing them just to arrest them again.