
What have you tried to stop him barking at kids, ie. do you tell him 'no' sternly, or 'check' his lead, does he pull forward wich means you have to pull him back to keep hold of him, does your heart sink and you feel nervous when you are out with him and are confronted by screaming kids etc... How you have been managing this behaviour can make a difference to his perpceptions of children, so again, I think it is definately best for you to seek proffesional help as you will also benefit from being shown how to handle him correctly in these situations.
He may be more than just fearfull, it may be that you have inadvertantly taught him to guard you. Either way, it's best not to mess about when it comes to dogs & children.
> There would never be a chance that I would ever let him near the children, he is always on lead
I don't mean to try and scare you atall with this, just emphasise the fact that it is very improtant to sort this behaviour out. My dog is always on a lead or long-line
(he is friendly but the look of him frightens people, so the DDA is always in the front of my mind), this has not stopped children running at him. I know kids should not be allowed to run up to dogs, get in thier face and bear hug them and it's easy to say, 'well you should have told the kid to stay away'. But I have lost count of the amount of times I have been caught of-guard and have a child chuck his arms around my dogs neck (eg. when I've just managed to stop one child running full steam into my dogs face, giving the child a 'dog-savvy' talk, while another child approaches from behind me and starts petting the dog). It would make for a much easier life for you & your dog if you knew your dog was not so reactionary around children. It can be done, it's not too late, but it is far to easy to get things wrong without proffesional help when you are dealing with an adult dogs behaviour that it has always had.