In a way it isn't that long until March if you think about it since it will be January before you interview someone interested and they likely wouldn't start till February at the earliest by which point the current interested family would be looking to integrate. At this point I would be inclined to firm up the March family and get them to sign contract and pay a non refundable deposti should they pull out - make sure it says that in the contract that they forfeit if they don't start and if they start are bound by the contract withdrawal rules. But at the same time let them know that the space will be open in January and let them pay on an hourly, half day or daily rate if they wish to use any of the days till child would start. Even if it is a couple mornings a week and gradually building to fulltime it would work for everyone.