Lynch Syndrome

Our family has just learned that my husband's maternal aunt has Lynch Syndrome. She has been treated for many different types of cancer since she was in her 40s (including colon), and now at the age of 87, she was told about this hereditary syndrome. My husband had one malignant polyp at the age of 50 and is monitored regularly.  My husband's mother developed colon cancer at age 79 and was completely cured with removal of the tumor. Our 41 year old son just had four benign polyps removed. We are concerned about this syndrome. Should our three children have genetic testing, or am I being overly cautious?