Can you hear the rattle when you bounce the front end or must you be driving? The best way to get to the bottom of a front end noise is to road test with the technician who will be working on your van so that everyone can agree on the noise that is to be repaired.
That is good, it should make things a bit easier. Have someone bounce the front end while you look around for something loose. Conentrate on the area where you hear the noise. The upper strut mounts would be a good place to start looking. Be carefull if you reach into the suspension area while the front end is bouncing, there are a lot of moving parts!