Why didn't the family go the day before to make sure? The day will be long and exhausting as it was planned. That is worthy of criticism!
Flying and doing all those activities in one day seems too much to me.
As a parent, what can you do?
You can tell kids -- beforehand -- that travel works most of the time but things can go wrong, so do not be surprised if they do. It is part of travel. It is OK to be disappointed. Whether things go well or not, we are polite and say "thank you" to the flight attendants and pilot for their work.