Where I live dogs are pretty much banned from being close to kids playgroundsn (usually 20m I think). And unleashed is only allowed in a very few places which is where we take our own dogs.
You have two alternatives
1. ask them nicely to get rid of their dogs or tie them up, depending on the rules at the park
2. Call the council ranger
I was at our local park last summer and there was a dog in a parked car. The window had been left open only a few centimetres on one of those really hot Sydney days. Was just about to call the ranger when the owner must have seen me looking in the car and turned up. He gave some excuse about it not being hot in the car - total crap,
