You may want to search for articles. There are a number of databases that could have useful information. If you don't find what you're looking for in the following databases, look for others in the A-Z Database List!
These are some Native American publications available online. Scanning these could give you an idea of current issues affecting Native Americans.
Considering you are putting your portfolio together for a young audience, you may find it useful to explore resources geared towards school children. The following databases may be useful, or look at the entire list of K-12 databases available to you.