Sorry, no idea about Rubik cubes! And I have gone to Science World for Body Worlds but have not stepped in their store.

For food, you could consider the Banana Leaf (Malaysian) on Denman near Davie. That location is tiny but for lunch it can be a nice option.

If you're willing to spend a little bit (ok, quite a bit) more money the Raincity Grill (also on Denman about across the street) is the home of the 100-mile menu and sophisticated food. This really hangs on how much you like (and can afford) fancy food. It's not downtown, but there is also the legendary Vij's on 11th just at the intersection of Granville, and the next-door Rangoli. HIGHLY recommended (and not very expensive).

Enjoy your stay!