"They are playing with their spoons and forks."
Translation:Mereka memainkan sendok dan garpu mereka.
Not a native speaker but from what I understand, bermain is the form without a direct object. In this case the object of the sentence is the spoons and forks, therefore we use the me-kan circumfix. Google translates memainkan to play, manipulate, fiddle [with] so if there's an object involved we probably use this form.