I think that you should add some activity completions for other items at key points of the course where you want to see progress on the activity completion report. Adding some automatic completion to simple things like videos, page, links, etc. can give you this with no interruption to course flow.
One trick I use is to have a simple Choice activity at the beginning of a course for students to answer some basic question, so that you can get a first interactive activity completion with a time and date on it as a starter. Or make them read the syllabus or accept some course specific terms and conditions, for example, but the goal is to mark that starting point of their work.
Another way, especially if you want to improve motivation and completion, is using Badges, again at some strategic points in the course. This is especially useful if the courses are long and take some time to complete, since it can help identify a reachable interim stage in a long course.
Randy