Sorry, but Harriet Tubman did not have any children with her first husband John Tubman, and so she has no Tubman descendants. John Tubman, who was already a free person, remarried after Harriet ran away from slavery in 1849. He and his wife Caroline (also a free woman) had several children together before he was killed in Dorchester County, Maryland in 1867. Perhaps your daughters are descendants of John and Caroline Tubman, or of other Tubmans from Maryland or Georgia. Check census and other genealogical records at Ancestry.com or Familysearch.org or any other genealogical website. Good luck!