My husband and I spent out mid-October honeymoon on Kauai!! We stayed at at Hale Nanea, a little cottage. It was a bit pricey-I am not sure what your budget is...we were only there for 6 nights. I would really recommend it--you could stay there for as a few nights and then stay on the south shore for the rest of your stay! My husband and I are in our early 20's and we did not find Kauai to be boring at all, it is a honeymoon after all...and we are going back to Kauai this summer!
website for cottages:
http://www.secretbeachkauai.com/

good luck and congrats!!!

Congratulations!
We stayed in Poipu - great sunsets and great beach for beginner snorkeling. We liked the south for the ease of access to the west (Polihale was awesome) and to the east/north. Definitely go to Maui tho'...very romantic. We stayed at a B&B there (Fountains)...high on a hill, but you drive everywhere anyway. Be sure to go to Old Lahaina Luau - everything you would want for a truly fun, campy experience. Maui has reasonable restaurants, great snorkeling sites, and alot of variety!