Technically they have to pay what your contract says...and your contract needs to be very clear and concise so there is no wiggle room to get out of payment. BUT, since I always have parents pay 2 weeks in advance of care I only had a 2 week notice needed...as it is much harder to collect 4 weeks of payment once the child is gone then the typical 2 weeks. If you want the money for the 2yrs old you will likely have to threaten to not provide care for the twins while they search for other care...so they have a reason to pay. They pay for all 3 spots or forfeit all 3 spots immediately. This again, will depend on what the signed contract states.