Reading the previous chapter I think there’s just a curse that makes going outside dangerous for them specifically? But the tone change between the previous chapter and this one is still a bit weird. Like would it have been fine for them to go out accompanied by an adult?
Famous version of Sleeping Beauty has the curse be inflicted on the Princess by a spindle, while the kingdom being put to sleep is the result of the fairies magic.
If we consider that this is loosely based on that version of the story, I don't expect this series to do everything the same, instead maybe some other object might have been the cause of the curse.
(so far the only thing thats the same as the source is the thorned vines, the kingdom put to sleep by a different force, and a prince from a different kingdom)