Hi Pat,
You've mentioned that you've considered using the Feedback activity for the consent form. Have you tried to put this activity on your Moodle site home page? In this case it will be available to all registered users on the site, not just people in one class.
If you use My home as the default home page on your site and not Site home (Appearance -> Navigation -> Default home page for users), many students might never visit the Site home page. To work around this, you can give a link to the site-wide consent form by putting in an HTML block with a link to the form in the default My home page layout, and of course the link can be shared in different courses all over the site.
Ravi