Can Employee’s Opt-Out of ObamaCare?

We are a golf course that hires mainly college aged adults as well as older adults that work anywhere from 20 – 40 hours a week. A couple of questions:

1. If the college student is already covered by their parents – my understanding is: that the student can opt out of our insurance since they are already covered. If this happens, can I work the student over 30 hours a week (which he would then be a FTE) and would I avoid any fines? What would I need to show to protect my business from fines? Can the student opt out if he would regularly work over 30 hours a week?

2. Same situation with an older man that is covered by his wife’s insurance. Do I have to schedule these workers less than 30 hours a week to avoid any penalties?