The ports of the calculator are meant for data. They can only supply a small current. It may be just enough to control a relay, but it's best to put transistors between them, just to be sure (or control the motors directly using transistors, if your transistors are powerful enough).
And in any way, don't forget to put a discharge diode on the relay (put a diode in parallel over the coil of the relay in the direction that it blocks incoming power).