Hi there,
One of the best museums in Portland have to be the
Oregon Museum of Science and Industry (OMSI), across from Waterfront Park. The
museum has many excellent museum exhibits for all ages, and it is an absolutely awesome place to take the kids.
You'll also find an Omnimax dome theater there, a real submarine to tour, as well as a planetarium. The best thing for me is that many of the exhibits at the Oregon Museum of Science and Industry are hands-on exhibits, so you can do more than just look at things.
Matina