I would reimburse the money for next week, but not the deposit.
"After a great deal of consideration I have decided that my daycare is not the best fix for xxxxxxx and xxxxxxx. Due to the disrespect I have received from both Mrs xxxx and Mr. xxxx termination will be in effect immediately.
A check covering your next weeks payment will be mailed to you by xxx date. (send it registered). Your tax receipt will be mailed to you by the end of February 2014."
Have all their things ready at pick up.