When you stop getting butterflies- that's when you should worry. That feeling after the fact of wondering what the big deal was is normal too. If you hadn't been nervous before the rapid, you might not have been on your game and then the afterthought would be, "why wasn't I paying more attention? I could've avoided that hole/sleeper/flipper wave, etc."
I've been boating about as long as you have, and I always get butterflies, even at high water on my town run that I've done a million times (literally). A healthy respect for the water can be your best friend out there.
And I agree, having my son in the boat raises that awareness exponentially.
"There is NOTHING--absolute nothing--half so much worth doing as simply messing about in boats. Look here! If you've really nothing else on hand this morning, supposing we drop down the river together, and have a long day of it?" -Wind in the Willows