The Skyliner will likely start running between 7:15 - 7:30 but I would still try to be in line between 6:45 and 7:00 as you will want to be towards the front of the line. An 8:00AM ADR will be a little tight if the Skyliner does not start until 7:30 but you should be able to make it if you're towards the front of the line.