I don't believe Julia and Hiram were living with George.
George Crossland arrived Astoria Sept 1 from San Francisco aboard the California 12 September 1850, 3:1. Source: Oregon Spectator Index 1846-1854.
In 1850 the family was living in Marshall Co., IL. Jeremiah Feasle, 69. Hannah Feasle, 63. William Feasle, 20. Jeremiah Feasle, 18. Julia Crossland, b. OH, 24. George Crossland, b. PA, 28, cooper. Hiram Crossland, b. IL, 2.
I wonder if George went to San Francisco first to scout prospects about moving and then on to Oregon City where he died.
I didn't find Julia or Hiram in Illinois or Oregon in the 1860 Census.
George isn't listed in findagrave.com in clackamas county, oregon or Marshall county, Illinois.
You'll find many Clackamas county cemeteries indexed at interment.net.
The Clackamas County Family History Society, rootsweb.ancestry.com/~genepool/ccfhs.htm may have additional info. Successful Searching!