I was unable to identify which William and Clara Matilda Olson were the correct persons, but I did find the second request logged under this question:
In 1930 John & Alvina Larson lived in Katsap, Washington (U.S. Federal census). He was 47 and she was 45, and he worked as a logger in the lumber industry. Their daughter was 15 year old Frances, and their son was 14 year old Walter. The census listed their immigration dates wrong by one year, but I'm sure this is the person you were looking for.
In 1920 they lived in the same county (Kitsap), in the district of Waterman, and they lived on Waterman Valley Road. Their children, Frances E. Larson was 6 years old, and their son, John W (Walter) was 3 years and 3 months old. The census was taken in January 1920, so you can tell from that approximately when John Walter had been born. On that census he said that his occupation was farmer, general farm. They owned their home without a mortgage. The wife's name was spelled incorrectly as Elvina.
I am not very good at finding people in the social security death index, so perhaps someone else can do that for you.