Plumbing for Outdoor Kitchen

I'm doing a pretty large "remodel" of my back patio involving a whole lot of retaining walls and a new patio surface. I'm still planning out the layout of my "kitchen" which will include a gas grill and a sink (and a sweet brick oven), but I start digging for the walls this week. The utility lines need to go in before too many walls get in the way the patio gets covered.

I know very little of the "right way" to plumb an outdoor sink. It is in Seattle, so our "frost-line" is non-existent. Even though the ground doesn't freeze, the air does freeze here occasionally so I do need to worry about pipes. All the water lines I've ever dug outdoors are @ 24" depth and don't pop their head up to any fixtures until they're inside.

Can I just treat it as a hose and put a valve back in the house and shut it off for the winter? Or do I need better frost protection? Maybe there's a better option that lets me use the outdoors even in the winter (even though it may freeze a night or two in the winter, it's quite reasonable to be outside many winter days here). Any issues with running hot water too? (He asks knowing there probably are...)

Just for completeness... The sink will be a concrete cast (i.e. mostly weatherproof), no fixtures chosen yet, location will be about 20' from the house.

Thanks in advance for any ideas, warnings, or horror stories

It's not likely that the pipes would freeze buried 24" deep, but where they come up for air, they can and will. I would not risk leaving water in the lines even in the relatively mild Seattle climate. Just turning the water off in the house as you mention will be a good beginning, but this will still leave water in the pipes unless you drain the lines. If the lines are sloped back into the house, you can put a tee in the lines immediately after the shut off valve and install another valve in that tee as a drain valve. This would valve would be opened after the water supply was shut off, and the water in the pipe then would drain back to the house. You could use a hose, but a 5 gallon bucket would work to catch this water. This is simple enough that if you could use the water once in awhile during the winter. If it would be difficult or impossible to slope the lines back to the house, a small air compressor could be used to blow the lines out.