At least they cancelled and didn't just "no show." But that's still gotta be just so frustrating! Maybe it'll be better in the spring, or whenever it is kids finish school for the year here?
When I was selling my condo in California, the agent would give us a warning phone call 30 minutes in advance. So the house always had to be completely spotless. One day I was at work and the daughter was at home having a pizza for lunch and got the call. So she tidied up and left, but forgot to take her pizza box off the floor in front of the TV. The agent who was showing called our agent and was saying that the house was "a mess" and so our agent phoned me and gave me a ration for leaving the place a mess, and how the hell did I expect to sell it like that. I went straight home and the only thing amiss was the pizza box on the floor. The place was otherwise pristine.
Often times other agents (buyers agents) would just show up with them unannounced, even though the listing said we needed 30 minutes warning and they were supposed to be contacting us first through our agent. (The daughter was working nights, so she slept very late. This caused quite a bit of trouble for us.) We even had a few show up after we took the place off the market, unannounced, and want to tour the place.

On one showing, they must have had kids with them because toys and things had been moved around, and someone got into a bag of (unopened) candy we had on a shelf. We know that the same person came in a few times, because he left a stench of BO in my daughter's bedroom that was unmistakeable. I used to wince over that, wondering what the hell he'd been up to! (Seriously, same smell.) Probably was the one who gave us the lowball offer. (That we rejected - it wouldn't have even paid off the mortgage.)