If they are molded ABS plastic, MEK will fix your cracks.  I've talked about the MEK for plastic dashes quite a bit.
Basically, you'll take a cheap crayola paintbrush, and brush on the MEK.  Make sure the two sides of the crack are firmly touching.  The MEK will essentially weld the plastic.  Virtually invisible, too.  I used it all the time in cracked vehicle interiors.