Those are two great islands! (which isn't anyway, huh? :-) ) We get pretty laid back when we go there. Hanging and laying around the beach and golf are some of the highlights.
(Oh, hey. . . Depending on which course you play, try not to bring "white" shoes. The red soil is difficult to come off, especially when it dries on.)
Maui - Paia is a nice little surfer town. Paia bay/beach is out there. A friend lives there- fun hang out with lots of little ethnic restaurants- inexpensive. On its beach, they have bigger waves and can be a lot of fun if you like surfing, paddleing...
Snorkeling in a half raised volcano, Molokini. The trip out there in a catamaran who provides the gears, lunch and beverages is half the fun. The Prince Kuhio or other newer boats, they're fun, too- safer actually when there are white caps you could run into.
A day trip to Lanai. There are two courses if you want to bring the sticks- The Challenge at Manele is by the ocean, the other is up top the hill, they are Nicklaus and Norman. My wife and I spent a day at the public beach there- we took a cooler and a blanket (while everyone else had their golf bags... ugh, I was so jealous). Very good snorkeling there. Not much of restaurants... you have to get up to the hotel.
Honua Kai is a great stay in the Lahaina Area (almost to Kapalua):
We've also stayed at small places and they are very nice, comfortable, clean and friendly people ran it.
Over in Makena side, it's gorgeous there now. The new developments are nice. Grand Wailea and the Ritz are out there.
Drive around the two sides are alright. The roads passed Kapalua from Lahaina (northwest bound) gets real tiny- like we had to back up a quarter mile on a zig-zag road (no rails) once because of a truck with a load. The scenic views are alright, but I wouldn't do it again. If circling around the Hana Point and the volcano side, listen for warnings on volcano side- it's closed sometimes! I wouldn't do that again either.
Nightlife are mostly in Lahaina... we don't go there much... too busy.
Kauai - If you are staying at Princeville area, closer up the Napali coast, there's a nice hike from the end of the road and it takes you over a couple of hills. The hills can be a tough hike with a cooler or heavy load. But the hike is fun and there's a nice beach out there to lay into as a reward... but not much. There are a lot of people who goes through the trails nowadays.
From Princeville on your way up to the end of the road, you'll see a lot of little restaurants where you can plan your lunch/meal. I can't remember the name of the restaurant we ate at, it was vegetarian, (I'm not) but the meal was amazingly great!
Oh, if you like raw fish, Yelp out for Poki-Poki house... :-)
Korean barbecue has been popular out there in the later years. It's good! It's short ribs, bone in and marinated in bbq sauce.
Ocean rafting tour is cool and it's a lot of fun! For me, the smaller the raft, the more fun it is... specially when the captain feels like taking the group into a cave as he uses timing rhythm tempo with the wave to get in and out of the cave. . . weeeeeee!!!! Whale watch goes with it, lunch and bev, of course.
Never done the heli ride... no thanks.
Didn't do the zipline either...
Nope, not the quad...
If you are in Poipu side, Old Town... look out for a shrimp truck! (lol) nothing fancy but so delish. . . :-)
It's the dry side of the island or desert like, but beautiful beaches, too!
For a nice dinner, my wife and I like to visit an old restaurant for it's good food, service and its style.
Sorry, their web seems to be having trouble, but here's their yelp page.
Wishing you a happy trip!