A simple (but up-front costly) method might just be to use DreamWeaver and enable "Templates." I ended up doing this for client
Wasatch Community Gardens since DreamWeaver was what they preferred. Once a template is created and the proper variable tags included (for custom header, content, etc...) any update to the template is instantly propagated to all files based on that template.
If you want your dad to be able to update everything on his own, I'd just go with a stock hosted solution, like WordPress, Blogger, or Tumblr. Free, lots of space, and they all let you do custom templates.
Re: Joomla
Joomla's a small install size (couple of megabytes) and is completely themable. Templates are HTML/CSS inserted into a PHP file. Design can be done using just the HTML/CSS and then quickly modified to include the PHP tags. You'll need to make sure that free server has PHP and MySQL installed and running, though, as well as insuring you have read/write/administer access to at least one MySQL database. It's install is one of the more graphical ones, but they're all pretty much the same: setting up the MySQL database connection and making the administrator account.