The main event takes place in The Hague with Prince Willem Alexander leading a parade of 3,500 military personnel and veterans through the city. There will be a fly over (good to see from the Malieveld) and a stage hosting musical acts throughout the afternoon. The police also give demonstrations there, and every type of military vehicle is available for a good look over.
I have attended this event twice now and it is definitely worth a trip out to experience the atmosphere of the day, particularly if you have a little boy or two in your family!
You can find out more, including the route parade and timing and location of events on the website http://www.veteranendag.nl/n/6/Home.html