Though there's a ton of information on this site that only works with a subscription or a purchased copy of the textbook, there's some good free content, too. Click the "Lesson Plans" icon at the bottom right of the home page or select the same option from the "Resources" drop-down menu at the top of the page; that's the best bet for accessing free resources. These lessons are nicely aligned with holidays and observances (such as a Presidents' Day section and a Black History Month section), nicely cueing parents to useful times of year to access this information. The Lesson Plans vary in quality and complexity; some, such as the "Citizens, Not Spectators" content on voting, is especially extensive, with three-day, five-day, and extended lesson plans available for the fall or spring election cycles. All elements of this section are extra-detailed and good for all grade levels; they're clearly meant for the classroom, but parents could use them to seed rich conversations with their kids, too.
The Black History Month section is dense but looks dated, and some kids (and their parents) might be underwhelmed by the format. Other lesson plans are interesting but less detailed; the Presidents' Day section focuses on four presidents, comparing them head to head on two key concepts: their contributions to American constitutionalism and citizenship (Washington versus Madison) and their use of executive power (Lincoln versus Reagan). Other lesson plans are less strong, though; some are only PDFs of the publisher's book chapter plus a few worksheets. Additionally, the "We the People Resource Center" is also a great resource for kids studying history: Though it's technically a companion website for the third edition of the Center's textbook of the same name, it's also a good-but-dated resource website for exploring terms and concepts related to American democracy and citizenship. Overall, this isn't the slickest website, and it's likely most useful for kids whose classes are already using the accompanying textbooks. But, if you're looking for some stand-alone lessons on the voting process or the Constitution, this site is definitely worth a look.