My fiance and I are planning a May honeymoon to Hawaii (neither of us has ever been) for 11 nights. We are planning 6 nights on Kauai at the Princeville Hotel but are struggling with where to spend the additional five nights: either Manele Bay Hotel on Lana'i or the Four Seasons Haulalai on the Big Island. Kauai will be the 2nd half of our trip so we want the first 5 days to be VERY relaxing since we will just be starting our honeymoon. Any thoughts or comments would be greatly appreciated.

I suspect you're locked into your Kauai dates from your note, but if all options were open, I'd spend the FIRST 6 nights in Kauai if you want to completely unwind. It's a very relaxed atmosphere, easily the most picturesque of the islands, and a great starting point.
BUT...if you're finishing up there, and you definitely want quiet for the first half of your trip, Lanai is VERY quiet and the 4S is QUITE relaxed. On a scale of 1-10, 10 being very quiet, I'd give Lanai an 11 and the Big Island around the 4S a 9.5.
Frankly, unless you're an entomologist, pathologically antisocial, or haven't spent time with your fiancee in the past 12 months, I think 11 days on Kauai and either of the other 2 will leave you bored.
For a change of pace, why not throw in a few days in Maui, or even (dare I suggest it) Oahu? Interisland flights aren't that expensive if you're in a budget framework that allows you to stay at the Princeville (a great property). There's such a difference between Maui/Oahu and Kauai/BI/Lanai. And the resort selection on both Oahu and Maui is outstanding.
Just a thought. Good luck!

I have stayed at the Four Seasons Hualali and at the Manele Bay Hotel and much prefer Manele Bay. The Four Seasons has several nice pools but no real beach to speak of, whereas Manele Bay is arguably the best beach in the state.
Manele Bay's cuisine (as well as that of its sister resort, the Lodge at Koele) is second to none (although quite expensive). Lanai is about as relaxing as it gets and you have complimentary access (via a nice 10 minute shuttle bus ride) to the facilities of both resorts. The resort itself and its setting is, in my opinion, far more attractive at Manele Bay. By the way, 6 days at the Princeville will be a long time, unless you are a golfer...it is in a beautiful setting, but is rather isolated and is on the wetter side of Kauai.

Why not Maui? Maui is the best Hawaiian island by far. There is plenty to do, loads of scenery and activities and great restaurants. If you want to relax you can do that on Maui, but if you get bored relaxing, it's nice to have all the options available. Lanai has nothing to do. Big Island is not nearly as pretty.
Maui is the best.
LOTS more info about Maui restaurants, hotels, activities, sights, etc, at this web site:
http://www.mauihawaii.org
(note it ends in org, not com)
Jon

I live in Oahu, have been to both many times, and it depends on what you are looking for. If you want a beach with snorkeling, you'd have to go to Manele, because the beach is mediocre at the Four Seasons and you can't really go in the water. If you want to be pampered, the Four Seasons wins hands down. The service, staff, and amenities are a notch above most all resorts in the state. Manele is very nice, but has a large resort feel(as does Princeville), while the Four Seasons has a more intimate feel to it. Food and golf is great at both places. The athletic facilities/instruction is better at the Four Seasons. Please contact me if you have any questions.