Have you already booked your trip? We just returned from our second time in Kauai. It's such a beautiful island, but personally, I think 10 days is a little long. I would split my time between two islands, such as five days on Kaui and five days on Maui.
I don't have an idea for rustic lodging--you may want to check with Tripadvisor or just Google "rustic lodging in Kauai." We stayed at the Marriott Beach Club and loved it.
Make sure you eat at Duke's restaurant, go to Princeville. We also enjoyed the Fern Grotto boat ride.

I/we love Kauai - and you could easily split your time there - with a week or so at one end of the island (you can sometimes get better deals on a weekly rental) - and the rest of the time at the other side.

While we love the North Shore, and in early Oct - it should still be fairly calm - but the waves might start to kick up a bit - so perhaps a week down in sunny Poipu would be the best for beach lounging/swimming/snorkeling - while you could also enjoy the beauty of North shore for a few days.

If you really want "rustic" - check out renting a mountain cabin up at Kokee - Waimea Canyon area - the Grand Canyon of the Pacific as Mark Twain used to call it.

A couple of days up there with hiking and all is also great. http://www.gohawaii.com/kauai/regions-neighborhoods/west-side/kokee-state-park

Just so you know - Kauai - the "Garden Isle" - is the smallest of the 4 main Hawaiian isles, and easy to get around - and from the North Shore - at Princeville/Hanalei - down to the south end at Poipu - is usually not much more than an hour - and on to the "Grand Canyon" is about a nother half an hour where you start up the hill.

That is - unless you hit the "rush hour" commute in Kapaa/mid-island - and that could slow you down a few minutes - but there is a "bypass" that you can find around Kapaa town - which is pretty much shown in all the tourist mags you can pick up at the airport - which have good, fold out maps.

Have fun in Paradise.

But hey - I always am one who likes to see as much as you can the first time, so yes, you could split your time between two islands - Kauai - and say Maui - or even Big Island - which is our second favorite.

Actually - Oahu also has a lot to see and do outside of Waikiki - and we love all the islands.

Yes, you have enough time to split your stay. But there's MORE than enough to keep you in bliss for ten days on Kauai. (I'll be there for the entire month of October--and I promise I won't be bored.)

FYI, those cabins in Koke'e are REALLY rustic--meaning like camping--but with a roof over your head. I wouldn't suggest staying there more than one or two nights because you'd be quite far from anything other than Waimea Canyon. You'd have at least a 30 minute ride down a windy canyon to get to the main road.

Ten days is not too long to be on Kaua'i! We once stayed on the N Shore for a week, then moved to the kalaheo area for three more days...that was a great combination.

Hanalei Colony Resort on the North shore is very laid back. http://www.hawaiirevealed.com/free-travel-info/kauai/kauai-resorts/haena-area/hanalei-colony-resort
The location is beautiful and puts you close to Ke'e beach, beginning of Kalalau trail, Limahuli Gardens, tunnels beach, and not too far from the town of Hanalei for several restaurants and shopping. A week at HCR is heaven for me!

Waimea Planation Cottages are actual former plantation workers houses http://www.hawaiirevealed.com/free-travel-info/kauai/kauai-resorts/waimea-area/waimea-plantation-cottages
This would be a good base for going up to Waimea Canyon, Koke'e and Kalalau lookout, as well as the towns of Hanapepe, Koloa, and Po'ipu area beaches.

ALOHA you gave some good suggestions on low key places. I agree that staying up at waimea canyon for more than 2 days cuts you off from the rest of the island. 10 days is perfect. actually we like to rent Condo for a week and then check into a lovely hotel and be pampered for a few days before we go home. Let someone else make our bed and clean the room!

Thanks to all who offered advice!