I also do annual receipts for the same reasons - parents lose them, parents lose them and think they didn't get them, doing it once is less time consuming that 26 times a year. CRA are fine with annual receipts but they must be issued by end of February.

I also tend to issue the final receipt if a child leaves mid year on their last day. But again, CRA says this can wait until end Feb too. It's up to you.