They need the children’s names
I was thinking about what the MIY said about things needing to be done the right way, and having the bones not being enough.
Then I remembered a conversation in season 1 episode 4 between Julie and Trudy about a pillow. Trudy says “The things that matter to you should always have names”.
It got me thinking, maybe that was a hint that they need to remember the children’s names before they can complete whatever ritual it is they need to do to escape. Or Maybe Julie will story walk and learn the names.