Somebody a while back posted a report about this:
http://kapitiislandnaturetours.co.nz/

Have you been here:
http://www.sanctuary.org.nz/

More:
http://www.doc.govt.nz/parks-and-recreation/tracks-and-walks/wellington-kapiti/a-z-of-wellington-kapiti-tracks-and-walks/

Yes, I made it to overnight on Kapiti. Loved it.

http://www.fodors.com/community/australia-the-pacific/kapiti-island-lodge-photos.cfm

Minnie found us a kiwi within minutes!

The website in my post will link you back to the one posted by Diamantina, it's the same place. Booking the permits and launches can be a bit confusing, so if you do go for the overnight I suggest emailing Minnie first. Allow some lead time since they do sell out.

Thanks so much for the great suggestions--and pix.

I bookmarked the walking trails.

I don't think Kapiti Island will work for an overnight. The lodge seems a little too rustic for DP -- who insists on an en suite bathroom. But a day trip might work if we stay based in Wellington.

I've driven up the Kapiti Coast and enjoyed some beautiful walks -- but haven't been to the island.

I've been to Zealandia and LOVED it. Sooo beautiful -- and so close to the city.

PS. Diamantina -- I loved the koala post!

Mlgb, your post made me so excited about an overnight to Kapiti. I've got to do this next time I am there. I love Wellington, the city itself, reminds me so much of my hometown, San Francisco. Love driving over to the Wellington suburb of Eastbourne. Last time we were there we took a hike in the hills above it; it seemed worlds away from the hustle and bustle of the city.

It's really a shame that there are people out there who would give up an experience like Kapiti Island because they can't walk 25 feet to the bathroom. What do they do at work, I wonder.

Yes Diamantina, I highly recommend the overnight. Kiwi spotting, dawn chorus and the parakeets and saddleback singing right out your door. And the freshly caught fish I still remember ( I even liked the paua/abalone fritter).

These are my favorite "quick trips" around the Wellington area:

Castlepoint - Beautiful Scenery, lighthouse
Putangirua Pinnacles/Cape Palliser
Red Rocks Reserve/Sinclair Head (in Wellington)
Wineries - Martinborough
Kaitoke Regional Park

I hope you enjoy your time here!

Thanks for the suggestions!