You should ask your mother or father to give a speech at their Retirement Party. It just so happens that retirement is both the end end of a big adventure and the beginning of a new one. So, a speech that makes sense and uses all the knowledge, skills, and experience will be helpful to other people.
You could offer to help your parents get a map and go to all of the places he has worked. Every step along the way, from the one that led to him getting his first paycheck to the one that led to the happy ending, is a big deal. Make sure he remembers those times as often as he can.
Carefully chose an appropriate gift for the retire so that you can remember this important event. Thank your parents for their years of service and recognize their work with Retirement Gifts. This could be anything from funny t-shirts to mugs or wine bottles.
Because of the demands of their jobs, they may not have been able to do all of the things that were on their original Bucket List. Whether they want to go on a trip to their favorite place or try something new, the time is right for either.