Day Walks with Dogs & Young Kids Launceston area or Nearby?

My sister in law and her Husband and their dogs want to go for a day walk while they're here with my wife and very young kids. (I'll be elsewhere that weekend). I think something between one and three hours and not too difficult or steep and obviously where dogs will be acceptable.
Any ideas of suitable walks not too far from Launceston?
Any ideas of suitable walks not too far from Launceston?