I make out receipts in January and let parents know that they are ready. When a family leaves I tell them that it is their responsibility to let me know if they have moved. At the same time I will not mail out a receipt without first speaking with the family as I don't want the information in the hands of strangers.

If you give the receipt now there is a great chance they will lose it and want another one anyways.

By law you are required to give them a receipt by the end of February of the following year so you have until Feb 2014 and I would hold out. Make receipts for everyone at the same time.