I haven't found the marriages of Jennie O and Edith M, butperhaps since posting this you have resolved the question.
A relative of yours (seemingly) has posted much information about the family on this Genforum link, which I suppose you've seen, but if not I will supply the link here: http://genforum.genealogy.com/norway/messages/13935.htmlhttp://genforum.genealogy.com/norway/messages/13935.html
A responder to the above is working on the family history also and he lives in Massachusetts.
Here is the 1910 census to which you refer. Good to name the Christofferson siblings in this thread, since they could possibly be clues to the future identity of the Anderson daughters (a long shot, I'll admit).
1910 Acton, Middlesex, Massachusetts Anders Christoffeson 40 born about 1870 Annie 29 Carl A 10 Edwin H 9 Ellen M 7 Margaret J 5 Ella M 3 Alton E 2 Jennie O Anderson 11 born in Norway immigrated 1902 Edith M Anderson 5 born in New York Kasper Christiansen 24 Ole Christiansen 28 John Knisage 28 Pauline H Benson 20