So, is this supposed to mean "the mother's sleep" or "the mother is sleeping"?
("lala" by itself doesn't seem to be a verb, and if is means "sleep" (the noun), the sentence doesn't make much sense, right?)
Never mind, I just saw that it is a command, in this case, please add a comma, or at least an exclamation mark "Mother, sleep!"
I think kulala alone literally means just lying down. But its used in the way of sleeping because people like to shorten things.