child to give evidence via dvd link?

[jenks28]

My 10year old was hanging about with friend, he entered into the house of one of the lads a 15year old. at the address the 15year old unlocked a gun cabinet and produced a mixture of guns. this lad then allowed my son to handle them and then fire one in the back garden. I am horrified at the fact no one actually got injured.
Later that evening (10 hous later) when my son was in bed this lad along with friends committed a serious crime and are awaiting sentance.
My son has given the truth accounts of this day and the police have told him he is lucky not to be procecuted for firearms offence. The CPS say (wouldn't be in the public interest) but require a witness statement via dvd link? do i need help or is this standard practice? sorry if i seen nieve but we have never been in trouble with the police.