Advice on family-friendly Belgium?

I'll be in Belgium soon for a week on vacation (mostly).  If you've been there – or live there – what advice would you give on interesting things to do for a family?

We'll be based in Brussels; Bruges and Antwerp are likely day trips.

To give you an idea of things that have gone over well on past family trips:
Unique sites, casual but different dining, museums – what most trips focus on, right?

Since my first trip to Asia in the early 80's, the world has gotten "smaller" for everyone.  I see two primary factors: efficient global product distribution and digital content/connectivity.  People used to load up their luggage with Smarties in London or Coors in Colorado before returning home. I remember going over to neighbor's houses to watch vacation slide shows.  Not anymore.  You can get durian at the local Asian grocery or visit Red Square from your desktop.

So what's to be experienced in Belgium that remains unique, worth being there in person?

Thanks for your advice!

UPDATE: Had a great trip! If you're interested, you can see the slideshow on Flickr.