It is important to Let Kids Make Their Own Decisions, even if they are bad decisions (I think). As long as no one is getting hurt, and the consequences are not far-reaching, it's good to let them make some choices (I think). At the very least, if things go badly, they CAN'T BLAME YOU. There's something to be said for that.
Yesterday, here in the Greater Seattle Area, we had Sun. My car thermometer read 56 degrees, and things felt positively balmy. I packed my Corolla, clown-car style, with Clover (+ a friend), Neptune (+ a friend), the Large White Poodle, and myself, and we headed off for the park. This particular park is right on the lake, and after some playground frolicking and tree-climbing, Neptune was ready for something a little different.
"Can I go in the water?"
"Well, I guess so. I think you'll end up pretty cold and uncomfortable, but it's your decision to make."
And so he ran off into the lake, getting progressively wetter. Every now and then he'd yell back, "Can I go deeper?" and I would explain, again, that it was his choice to make, but that X, Y, and Z would be the consequences. (I did, however, draw the line at full body submersion-- there's no way I wanted that in my car on the way home.)
Soon it was time to head home. Strolling slowly back to the car, complaining cheerfully of the temperature and the rocks and sand stuck to his feet, Neptune grinned at me.
"I'm freezing! And my feet hurt. Why do you let me make my own decisions? I'm a kid! I'm young and stupid!"