movie title help

I know that I am posting on a different movies board....but...this was the closest western i could think of that might have had the same viewers..all i can remeber is that it is about a family traveling west, the two daughters get a fever and end up dying, they have to bury them along the trail, the mother basically goes nuts for awhile seeing her two young daughters images everywhere, and then they adopt a little boy that the mother totally resents at first because he keeps getting into her dead daughters toys....but ofcourse happy ending at the end.....anyone have any idea what i am talking about????

Thanks!