The only time there would even be close to an issue with the names is if you check-in at the counter with someone to check ID's. If the names are the same and it's just a matter of a typo there will be no issue. It's domestic I don't think it's a big deal. Common sense will apply in this case. If somehow you made a format error with the names it will be obvious and the agents won't take issue. It's not like you'd be trying to travel under vastly different names.

If you check-in via the QuickCheck kiosk using your QF FF card then that shouldn't be an issue. Actually you doin't even need that - just the booking reference number and your surname, which you know.

As for the seating, more likely than not given the 3 of you are on one booking you will all be seated together in one row, specially since the 737 seats 3-3 in the back. If you really want to change you can do that when you do online check-in.