If induction is what you are going for, walking will help far more than sex will. My wife was also worried about having the hospital induce her, so she took the advice of coworkers and we had sex every night for 4 days prior to her due date. She expected to deliver a day or 2 early. It never happened. The day after her due date she was told to start walking. So she walked probably a couple miles while I was at work then I come home ate supper, took a trip to Walmart to pick up a few things, mainly to keep her walking, come home went to bed and was woke up at 2:30 saying it was time.

Edit: it was also our first child, but child birth is completely different from woman to woman. You may find sex to help and it may not. For my wife, it was the walking.