Question about nanny pay schedule

I will hire a Chinese nanny to take care of my infant baby. If I am paying her monthly, am I obligated to pay her at the end of each month? Is it OK if I pay a week late? For example, is it OK for me to pay her August's salary on Sept 7?

The reason I want to pay her a little bit late is because I want to make sure she will not quit her job suddently. I told her that if she wants to quit, she should give us 2 weeks advance notice, but I am not sure if she will absolutely do that. It is not easy for me and my hu*****and to take a vacation without sufficient notice to our employers. So if the nanny quit suddenly, this will leave us into a very difficult situation. On the other hand, I don't want to appear to be an unfair employer to my nanny. So, for anybody who has hired a nanny, do you know if it is normal to pay nanny a little bit late each month? Is this acceptable?

Thanks!