Ancestors of Tasmanian McMahon and Sullivans

Interested in the family of Ellen Sullivan who appears to have married Terence McMahon February 1833 at Shanagolden. Children of above appear to have come to Tasmania (van Diemens Land) in 1854 on barque Northumberland. Children (Terence and Mary Mc Mahon) may have been in workhouse in 1851. Also interested in Ellen's sister Ann Sullivan who appears to have come to Tasmania with children. Also interested in Ellen's sister Elizabeth Griffin (nee Sullivan) who appears to have sponsored children and migrated to Tasmania around 1837.