Good wiki app for iPhone?

Gina and I are taking the family to Costa Rica in a couple of weeks, and we have a lot to do to prepare for the trip. Gina suggested that we should create an online collaborative space in which to share ideas and to-do lists. Her idea was to use a wiki.

I currently use a great little application, Evernote, for my own to-do lists, notes, saved web pages, and many other kinds of content that I want to capture, access, and edit later. It runs as an application on my Mac and on my iPhone, and automatically synchronizes the content between the two platforms. I have thoroughly enjoyed using it.

However, for the Costa Rica shared to-do list application, it has two shortcomings:

1. It doesn't run on Mac Tiger, only Leopard, and Gina's Mac OS is Tiger. (She runs Evernote, but her laptop access is web-based, rather than via their installed application.)
   
2. It doesn't allow private sharing. It does allow content to be shared with everyone (and indexed by search engines), but not shared privately with specific individuals or users.

I recently received an email from Evernote describing their feature upgrade plans for 2009, and one of the items involved improved sharing. Here's what they said:

The public notebooks functionality that we launched in 2008 was a timid, first step in our ambitious plans for making Evernote a great tool for sharing your memories and collaborating with your friends and coworkers. In 2009, we're going to greatly expand what you can do with your memories, documents, files, photos and anything else you throw into Evernote. If you're the social type, we're going to grow up from being your external brain to being a telepathic-mutant-super-brain, but with good manners. Of course, you'll always have the option to keep any or all of your info totally private.

Obviously, they're being deliberately vague on their exact upgrade plans, so I built a wiki on PBWiki that we'll use for now. PBWiki is a traditional hosted wiki application, but it doesn't have an iPhone app to allow mobile access.

A search of the iTunes iPhone app store yielded nothing. Any suggestions?