Terms of termination

I have recently had to terminate for aggressive behaviour. The parents have asked for 2 weeks to find a new daycare, which I am fine doing. It seems to me that I would leave the spot open until that time, so would charge by enrollment for that period (and be avaible to provide care). But what if they find and start care sooner: should I ask now for x days notification before care ends (and payments end) if it is going to be previous to the 2-week date?

If I were going to be available to provide care for the two weeks, I would have them pay for those two weeks in advance and the remainder would be non-refundable if they leave before. Personally, for an agressive child though, I would not be willing to continue providing care, but only you know how bad it is and how much you and the other kids can handle.