This basically means 'go to sleep now' right? Or is there a better phrase to say 'go to sleep'?
it is a polite way of saying mother sleep now. "go to sleep now" will be like a command in kiswahili "mama enda ulale sasa" will be the correct translation.
Mama nenda kalale. au Mama tafadhali nenda kalale. "Mama lala sasa" is unpolite and bad swahili!
to say it is bad swahili is kind of incorrect. in every language, we have informal and formal. Mostly we address older people using formal language. "lala sasa" is used mostly to soothe/calm babies to sleep
Does DL teaches bad Swahili? I studied linguistics, I live in Zanzibar, I have a degree in Swahili language and literature and I know what registers are in languages. This sentence begins with "Mama" it isn't an order to a child or baby. Besides "Nenda kalale" (and similar constructions) is used by everybody and in every context. "Tafadhali" is used in formal context.