Don't go if you're seriously overweight.Don't go if you've neglected your cardio for several months, or six.Don't go if you're going to pass any and all water supplies without refilling any and all empty water bottles.
Do take two smart, loving children who have been camping, hiking, and canoeing since they were born.Do take two thoughtful, insistent young people who have trained as high performance athletes.Do listen to them when they say, "That's enough. Sit here in the shade. Drink the rest of the water. Rest."