Looking for info on Pederson ancestors

I am trying to find some info the Pederson side of my family. I know that my great great grandmother came to America probably with here children. Her husband died in Norway. My great-great grandparents were: Peter Olson born: March 14, 1795 and died: April 01, 1884 and Gurina Ceselie Olson born: April 28, 1822 and died: October 27, 1908. Their children were: Karen Martha Pederson born: November 25, 1849, Bergette Pederson born: July 23, 1853, Nickolai Pederson born: March 19, 1863, Grethe Pederson. I know there was one more child (a girl I think). I would like to know when they came to America or anything else that can be found out about this family. Thanks!