analytics/activity log per group by group

A few groups of people plan to use the web site I created with squarspace and I want to see activity log per group by group. Also, I want do so without uploading any private information such as email address to the web site. Is there any way to do this?

What kind of activity data do you want to see? And what criteria do you use to define your "groups"?

I'm guessing that you want to see basic analytics data like sessions, pages views, time on page, etc. If you don't want to collect personally identifiable information, then the only data you could know about people would be what Google Analytics or another platform would be able to provide. They do provide a lot of demographics info, but it won't be 100% accurate. 

The only other idea I came up with would be to use UTM parameters in your links to try to funnel different groups of users into your site. For example, if you're advertising to specific groups, you could track them that way.