Time needed to check in for domestic flight after stay in Beijing Capital airport Hilton

I arrive PEK at 18:05, and have a reservation at the Hilton at the airport. I know there is a shuttle bus to hotel. My flight the next morning to Guangzhou is at 7:35 am. How much time should I allow to check in prior to the flight? Do the shuttle buses from the Hilton run promptly? Will I be able to figure out where to go to check in, get a boarding pass, and check my luggage?

Thanks very much.