How to make term reports, easy to do (and secondly effective, and accurate)
I've always admired the Swiss' education system of teaching kids where they rarely have examinations, but rather through constructive assignments and homeworks to teach students. At a conference I've attended, I heard a quick introduction on gamification of education and I am trying this out with some students.

Here is what I proposed:
Assesments (excluding exams and final project, due to curriculum and school board constraints) have unlimited re-tests, limited to once a week.
0.5 credit is awarded for 50%+ and 1.0 credit is awarded for 80%+
At the end of the term, their number of credit earned is divded by total number of credits for a "term work" grade worth x% of their final mark
The goal here is for students to not worry about a 50, 60, 70, 80, 90 or 100, but rather track their progress through completion of content. I believe the unlimited retries gives incentive for students who are falling behind to realize early and catch up immediately, rather than later. This is to avoid the mentality of giving up because it is "too late" or "wait for next test".
 To some degree, I believe in the innate competitive nature of CS students transferred from love for gaming

I believe this method (with modification to suit your needs) meets what you are looking for.
Accurate enough to give a % mark because you track progression. Although I foresee multiple 100% with this method
Does not disturb students because they are well aware of their progress, and know they can make improvements rather than blankly stare at an unfortunate poor test 1
Quick and low effort - I just use an excel macro and export to show my class after each week their progress