Can I go on the bumper cars while pregnant?

No. But ask your ob, the bumping could cause contractions or worse could cause the placenta to separate prematurely or could cause neck or back problems which can happen more often due to pregnancy, you will ahae plenty of time to do bumper cars after you ahae delivered.
No. You should not ride bumper cars as direct/indirect trauma can cause premature separation of the placenta and lead to an obstetrical emergency - abruption.