Ivar Wind Skovgaard , Jun 23, 2003; 01:26 p.m.
As far as I know, the legal difference between children and adults is that children can not enter into a legal agreement without a parent's consent (there are other differences, average size for one, but that's beside the point).
In public places there is usually no need of an agreement to photograph people, and this of course covers children as well.
How people will react to it is a different matter, but I believe that's the way it is legally in most places, and in addition I believe that's the way it should be.
Regarding wether a particular photo of someone who doesn't appear to like being photographed should be made or not, that's a different matter and applies to adults just as much as to children.