I'm a paramedic in Vic, not sure of NSW regulations but they are usually pretty similar to ours... There are no hard and fast rules regarding transporting accompanying children in the ambulance in Vic, but there is certainly a preference not to.
That's interesting nickle, the crew I spoke to said there was a rule -no children. I guess it's much easier for them to say that than, it's at our discretion and we don't want to because we don't think it's safe. If they say its a rule, perhaps they get less arguments.

Kazzo - you're right, I'm sure nothing will happen!