One of my favorite things about living in the DC area is volunteering with Honor Flight, which brings WWII veterans from all over the country to visit the WWII Memorial. It's a special place, but even better when there are several busloads of veterans there to experience it with.
Our volunteer group has a website with the Honor Flight schedule (https://honorflightdca.com/schedule/) if you're interested in timing your visit to the WWII Memorial to coincide with the Honor Flight veterans being there. This schedule only includes the Honor Flight groups that fly in to Reagan Airport - there are others that fly in to Baltimore and Dulles - you can check out the complete schedule on the national Honor Flight website at https://www.honorflight.org/tour-schedule/.
These flights mainly come in in the Spring and Fall, though a few come in the Summer as well.