Ok so this kinda follows on from do animals know thread, but do kids know?

My girls have been acting up this week. Actually they have been feral this last week, and everyday they seem to be stepping it up a notch or two. Christmas and new year period wasnt out of our ordinary routine. DH swears that its because of the school holidays, but I doubt it.
Im starting to think that they 'know' whats going on, or that something major is about to happen. DD2 has started sleeping a lot longer in her bed at night, instead of coming in during the night, shes coming in round 6amish. Shes even getting her day sleeps down again, both girls are sleeping in longer too.
But mostly they are acting out, they even seem unsettled.

Do you think kids have an sense of the impending?