No problem, glad to help.

His son seems to have a basic understanding of HTML and CSS, however, if I had to guess is using a WYSIWUG editor to do the actual coding.  I am betting this is where most of the mix/matched tags is occuring.

A lot of what I pointed out is more in depth than straight HTML and CSS.   It's factoring in how much data actually has to cross the wire.   The heavier a site is, and the more round trips it takes, the slower it loads and so on.  A simple concept, but often overlooked.

A few other things are User Experience issues.  The founder can validate this by doing a focus group.  Show a bunch of people whom know nothing about the company the site, and see what they do.  The following book is a good guide to 'to it yourself' UX testing. Rocket Surgery Made Easy: The Do-It-Yourself Guide to Finding and Fixing Usability Problems.

Since this is a non profit, using a metrics package like Google Analytics can yield some useful information, and if it's not already in use (I didn't check), he'd be well served adding that package, or similar to get some in depth data on how people view his site.