I do not fully understand your question. Do you already have a working site which is incomplete, but some of the content and design is already there? Are you in a pure planning phase?
Well, nonetheless let me give you an answer. I do not know how much of your part is 'to program' that website, but I am a programmer, so I tell you my favorite approach. And that is: Use the smallest available 'chunk' which can represent your website (in a browser) and continually improve from that base. Then whatever part is finished, can be reviewed by the stakeholders easily using a browser.
That would mean the website must be built in some way. Which means that you need some kind of sources to build the site (content, style info). That source (like source code) should be best available in human readable file formats (Word format <> human readable).
If you have sources in human readable formats, you can use source control software (SVN, Git) to store these sources. Everyone can change them. The changes are kept in a history, can be reviewed, tracked, committed, rejected.
Source does not necessarily means HTML code or something like this. People who are only interested in the content, should be able to only see and touch the content files. The build process has to care about putting these files into something that is visible in the browser (html, php, I do not want to go in the details, this is not StackOverflow).
I love tracking all changes using source control, but I know that managers can be easily horrified by this (like I can be horrified by Word documents). So a lot of people have to agree to this concept.