Very nice - and I'm not really a \"museum type\" guy
I lived in the south bay for 20 years, and only drove by the museum. This was my first time inside. I enjoyed a self-guided tour. I downloaded the MP3 bits and put them on my iPod. Made each stop very interesting. I'm almost 50, and thought I knew quite a bit of history, but I learned a lot there.
I loved the mummies, and I loved a lot of the art.
As for the planetarium - I liked it because I could take a load off my feet, and get a bit of rest. It was really not all that interesting. I don't think it is interesting for any but the youngest.
But back to the museum....
It is definitely wheelchair-accessible throughout. Looks like the front stairs were recently poured over with a ramp. That kind of takes a bit of the look away. I used to like the look of the long set of steps. But hey, now folks in wheelchairs can enjoy, so it's OK with me. I'd have just added a ramp off to the side.
The artifacts were a lot of fun to see - everything from toys, to religious artifacts, to musical instruments.
Very peaceful to walk around the grounds too. We went when school was out, so I am sure that helped (by not having a thousand kids running about).
All in all, I really enjoyed my time there and recommend it.
If you want to take photos, no flash. I used a Nikon DSLR with VR lenses, and they worked perfectly for every exhibit. The auto-ISO ended up between 600-1600, and shutter speeds 1/6th to 1/25th. But the VR worked wonders. I assume Canon's IS would be the same.
Enjoy!