I find a camelbak with (diluted) gatorade works well to offset the whining. Also, cheetos are a big hit, or "kudos" bars.
i find that beatings work the best...
seriously, the absolute best ticket is to make sure each child has at least one buddy along for the hike...they don't even realize how fried they are...
Funny thing, by the time i've driven a mile from the parking spot, they are usually all passed out, snoring away in the back seat...hahahaha