Accessible Theme or know of a plug-in?

Hiya,

I’m currently looking at using WordPress for creating a website for a non-profit organisation. One of the most important features needed for this site would be accessibility.

Question for you experts: could you recommend any accessible themes?

Also, in the same vein, do you know if there is any existing functionality within WordPress or something that can be added which will allow the reader to increase / decrease font size? Many sites with accessibility as a concern now have buttons located on their pages that will “increase / decrease /return to default “the font size and change the font style.

Thanks in advance for your help / comments.