Sure! That’s exactly what Content Management Systems (CMS) software does. Joomla! and WordPress (using the WordPress “Pages” functionality) provide this “out of the box” and are available as “one-click” installs on DreamHost. There are literally hundreds of other programs/scripts available for doing this in varying ways and to varying degrees - some a “news” type scripts that allow you to keep an easily changeable section of a page for the updating of an section, while others take a different approach by simply provided a CGI facility for editing a definable area of a page (check out hotscripts.com for many such things).
You are likely to find that iweb is difficult to use, at best, in a traditional web hosting environment. It was primarily desigined as an interface/tool for .mac, and it does things very differently than the way traditional websites are constructed and managed.
If you search for iweb in these forums you will find quite a bit of discussion about its use on DreamHost, and several excellent suggested alternatives that might be of interest. Even for a “hobbiest”, it’s good to maximize the return on your investment of time, and many other technologies/tools will give you a much bigger “bang for your buck” in the long run than iweb.
Since you are embarking upon a learning process anyway,why not learn something that is universally useful rather than something that is particularly .mac oriented?
Both Joomla! and WordPress can do a great job of handling a site like this. WordPress would be great for a basic informational site, and provide a “discussion” vehicle via blog comments, but Joomla! would be a much better choice, as it has a good selection of user management tools, community related features, and a wide selection of extensions that would allow you to have a “public facing” site and private sections for discussions, photos, etc.