I would rather open early than stay open later that is for sure. Talk to them about the 6 am start and make sure why and how they need it. I have a 6:30 start but have a family that wanted 6:20 just because it takes the dad half an hour to get to work so he needed the extra 10 minutes to allow for traffic, getting parked and punched into work on time. But I also made it clear to them I would do anything after 6:15 as in don't try pushing it earlier so if you agree to the 6 am it can be 6:05 they arrive but not 5:55 kind of thing as in you will be refusing to open your door till your alarm has rung the hour or they may start pushing it unnecessarily.