I've taken Vinnie hiking with me in the past. He's a bigger yorkie (about 13 pounds) and can keep up with me for about a mile or so. And then he poops out. Definitely make sure to take breaks and if he is slowing down at all, carry him. Remember, dogs really want to keep up with us and will push themselves a lot harder than they should. Just watch him, especially if it's warm out.
Make sure to carry water, plenty of food, and I would take the nutrical too. Hopefully you won't need it, but I'm a big fan of "better be safe than sorry." Also bring a first aid kit with you that is specifically for dogs.
Finally, when we've gone hiking over rocky terrain, I've used doggy shoes - Neopaws are the best! (
Dog Boots Shoe Neoprene Jackets Dog Sweaters NeoPaws) They can really save your dogs' paws.