We have a similar situation, my parents live 12 hours away. MIL lives 5 minutes away. She comes over for dinner once a week but I would never call her up and ask her for help unless there was some kind of emergency, it just would not occur to me. DH does though, I work weekends and if he has something he needs to do that the kids should not really be around for (he had to do some welding on the weekend) he will not hesitate to drop them off at her house. If my parents lived close I would absolutely do the same, I just don't feel comfortable asking MIL.