Labor participation rates are based on people under retirement age, therefore boomers retiring has the opposite effect of what you claim, as the number of working age people is decreasing while the number of overall jobs is increasing. From 2008 to early 2017 we had jobs disappearing faster than the boomers could reach 65.
Civilian Labor Force is the sum of civilian employment and civilian unemployment. These individuals are civilians (not members of the Armed Services) who are age 16 years or older, and are not in institutions such as prisons, mental hospitals, or nursing homes.
I was surprised to learn this, but the numbers actually DO include retirees -- as long as they are not institutionalized.