OP,
If your neighbour's and their children are damaging YOUR property, there is absolutely NO problem filming them.
For readers concerned about this, pls google UK law.
OP, if you feel it would be helpful to film your property being damaged, state it clearly while filming.
"I am filming my neighbour's children damaging my property."
Obviously, you should speak to your neighbour first and ask them to cease and desist.
However, if they continue, you are perfectly within your rights to film your property being damaged deliberately.
Your children have been injured?
Those balls would NEVER be returned from me...and I am a serial returner of balls!
Also my neighbour's child plays basketball endlessly...no problem with it.
Another boy hits a ball against one of my walls for an hour at a time.
I have absolutely Zero problems with this as they are great lads, late teens, and are so plote and respectful requesting a ball back.