Generally speaking, a 4mo. old pup still naps quite a bit. Over the years, I've had many pups and have two now (one 4mos; one 9mos). IMHO, 4mos is too young. Consider also your pup's vaccinations. Since you'll be in "the wilds", check with your veterinarian - you might want to consider Lepto & Lymes vaccines. Normally, Vets like to space out vaccines so as not to overload a pup's immune system. Yours is not a tiny breed, so this isn't quite as big a problem. However, by 4mos your pup probably should have had all of its vaccines (including any which require second vaccines in order to develop a proper immune system response), with the possible exception of Lepto & Lymes. Keep in mind that any vaccines given before 12weeks might not have produced an immune response in a pup (antibodies received from the pup's mother might intefere with the pre-12wk old pup's own immune systsem response). so called "Kennel Cough" (Bordatella, a bacteria, and parainfluenza, a virus, plus possibly some other viruses) is an exception to the 12wk rule. Two doses, sometimes given as early as, 4wks and 8wks of age, but usually older is fine; though many Vets will consider the 4 & 8 wk numbers a tad too early - note that "Kennel Cough" is probably NOT absolutely necessary for your plans since your pup will have minimal contact with other dogs. Also, consider monthly treatments for heart worm (mosquito borne) and flea & tick (this might make a Lymes vaccine moot, but i personally still vaccinate for Lymes). Finally, your pup is still young and so might not wander too far, but until one's dog has advanced obedience training (off-lead recall in particular), unless you want to risk loosing your dog, don't take the dog off-lead. At home, at 50 meters or more, i could call my dogs off of cats, squirrels, etc. with a voice just slightly above speaking - not need to yell and sound angry. IMHO, if a dog won't consistently obey a spoken command (one command only - NO repititions of the comamnd required for obedience), they shouldn't be taken off-lead. I've seen too many State Parks and Forests with posters for lost dogs. You might also add in off lead obedience training with whisper commands (first with you in sight and then with you out of the dog's sight), like we used in the Military back in the early 70's, as a gauge of how much control you have over your dog. This might be used to gauge how well your dog will obey when distracted/"tempted" by the call of the wilds). Obviously, distraction training is very important for proper obedience training.
Talk with your Vet. about this entire plan and at what age your Vet. feels this planned hike is appropriate.
The prev. poster's astute advice on conditioning is well worth adhering to.
BTW, Australian Cattle Dog = great dogs. Good choice for a canine companion. Very intelligent. Often require a firm hand in training, but are very intelligent and can be highly trained.