This is not quite correct.
The parking lot at TTC never closes. But the Express Monorail & Ferryboat to MK do not run that early.
On most days, the Resort Monorail starts running at 7am; you would want to be there a bit earlier to get on the first train leaving TTC. There's no point in getting off at the MK and walking; just stay on the train as CR is the next stop.
On some days, the Resort Monorail opens at 8:30. On those days there should be buses running in it's place. See this thread for more info. It's probably worth it to park at CR for peace of mind if you have an early reservation on one of those mornings (generally Mondays & Tuesdays.)
Thanks for this info!