Have you ever wondered why the dance schools tell you not to film during the performance at the end of year concert?
There are laws involved; lots of laws as it turns out. There are child protection laws, issues of consent, copyright laws and laws about artists getting paid.
As this article discusses, when it comes to copyright you can actually buy a license to make it legal, or of course, you can buy the concert DVD/USB. You can also technically, be sued for not doing it. Either way, by buying the DVD or getting a license (and they're the same price roughly speaking) you have the memory as well as the peace of mind of knowing you're legit.
But...even with a license to make recording the music, choreography etc all legal, you're still filming other peoples children.
In this day and age we're conscious when our children are being filmed, particularly in public places by strangers. I know for myself I have been in situations where I have called the police because of the actions of an individual just didn't make sense and my gut said who they were and what they were doing just wasn't right.
Filming others people's children along with your own is an issue of consent; albeit in a concert situation you likely know those other parents and your kids hang around together.
It's all food for thought but perhaps the simplest solution is to put the camera or the phone away, sit back and actually enjoy the concert and be in the moment, and then buy the DVD to enjoy later with family who couldn't be there. Why? Because our kids enjoy it when they know we're present and in the moment with them.