Hi David
It is possible to do grade calculations for the seminar activities that add a value to the course grade. The course completion can then be based on the attainment of a course grade.
Seminar attendance fully attended is 100% of the grade so if each fully attended seminar was allocated a grade of 10 then to pass the course a course grade of 60 would be required for 6 of the 8 seminars.
Seminars can also have a grade manually allocated to make calculations simpler
Let us know how this goes
Regards