They are very good rock scramblers, I think the low center of gravity helps. You have to watch them very closely, esp. at first, because dogs are stupid about rockfall (initiating and receiving; there's a trail here closed to dogs 'cause of dog-induced rockfall injury), but I realized this year that I wasn't worrying so much about Gwynnie falling on rock. They learn. I belay them on dangerous log crossings, and I don't like them near cliffs, but I've gradually come to trust them more.
I want, essentially, a climbing harness for the dog -- none of those plastic buckles in load-bearing places -- and I want to be able to tie-in a belay rope at the chest sometimes (as opposed to at the back shoulders), so if the dog falls in a river and drfits downstream, its head will be held up and face-forward. You can do this with about 6-7' of 1/2" flat webbing, mark the center and make a bight there, then tie 4 overhand loop knots; this makes 2 big loops,one behind the legs, one before; both big loops slip over the head; you have to fold the front legs through the hind loop; then tie the loose ends to the first (smallest) loop, which is also the dorsal tie-in.
If you get one of those commercial harnesses, you'll see that you can copy it this way, no buckles required. Tie in at the dorsal loop or the X at the breastbone.

Hello and Welcome!!!!

Whenever I need to lift the dog over an obstacle that even a corgi can't handle, I say, "Corgi Toss", and the dog steps into position to be lifted. Pete will learn to recognize this as a standard command. I predict you will soon find yourself stopping at obviously insuperable obstacles to help the dog, saying, "Corgi Toss", while he blithely leaps over them, laughing at you.
Our dogs are sorta tenderfoots in loose beach or road sand, and some snow conditions. The sand gets in between their pads, irritating the soft skin. I was talking to a guy from eastern WA whose dog gets plenty chance to run around in loose sand, doesn't have this problem, so maybe they can get inured to it. I carry these "Pawz" booties for emergencies -- big rubber balloons that roll over the feet, essentially.
The dogs are usually off-leash on trail; I keep a quick-draw leash tied to the pack strap with a rubber band holding the slack. I always keep them leashed to me in at night in camp (coyotes etc.).
They have their own little sleeping pad and blanket. If you throw your jacket over them at night, you might want to tie a knot in the sleeves -- I awoke one night, checked on the dog, found Al had crawled into one of the jacket sleeves and was trapped, like a tight sausage. Suffocation hazard? Probably not, but...

Read Joanna Kimball's blogachondroplasia is dogs It's fun right now 'cause she has new puppies (Cardis). This post talks about why you need to take it easy with corgi puppies. Our breeder was quite firm with me about "no long hikes or big challenges until 1 years old"; Joanna's post details why. You definitely want to avoid growth plate injuries, particularly in the wrist. Don't let him be jumping down off high furniture etc.
I'd think gently hikes would be OK -- I never did understand what the big fuss was back then, I thought puppy = indestructible. But I guess he's just about made the 1-year mark, huh?
Look out for slippery floors, too; we put out nonskid throw-rugs on all the landing/takeoff zones.
Get him one of those 8" children's basketballs to roll around.
Once he's grown, you'll never be able to outwalk him.
FYI, y'know those double chest-harnesses they sell for dogs? I'm designing one that you can tie out of about 7' of flat 1" webbing, no buckles, weighs 1/4 as much as the one we bought (which doesn't work well as a walking harness, rubs a sore). I'll post it here in the collar FAQ when I've got it perfected. Basically a climbing harness. I need something to belay the dog on steep snow, scary river crossings, and fords.

I love to see corgis in the mountains.

Hi Dave and Pete!!! Edward is 9months old too and Gem is 1 yr...I just love them both soo much!!!

Welcome. You sound like proud parents! He is a handsome guy!!

Welcome Dave and Pete! I know just what you mean about that irrational corgi love...I fully understand, Pete is such a cutie!