Keeping access to movement as simple as possible, I would highly encourage you to consider a hobby servo (sometimes called a servo motor or microservo).
Most motors require far more power than the power ports on a microbit can supply on its own. Also, controlling direction on a motor also requires some kind of motor controller, as is available on so many breakout boards, but that would necessitate another separate purchase.
Although I have never personally controlled servos without a breakout board and separate power supply, I have seen other teachers connect a hobby servo with alligator clips directly to the clip attachments on the bottom of the microbit (microbit powered by batteries, not just usb).
Hobby servos can be coded easily to move to specific angles, with a range up to 180 degrees.
I see that Adafruit sells servos with alligator clips and Sparkfun sells adapters from standard servo connectors to alligator clips.
Adam Singer (he/him)
Technology / Maker Educator
Maker Tech Lab
Davidson Middle School
Twitter: @DavidsonMakers
Instagram: DavidsonMakers