The fonts (typefaces) you choose will have an impact on the legibility and perception of your charity's publication.
A serif font has horizontal marks (serifs) at the corners and tips of letters. Serif fonts, such as Times New Roman, are good for large blocks of text as they are easier for people to read.
Sans-serif fonts (i.e. those without serifs), such as Arial, look cleaner and more modern. They are less legible, so are best suited to smaller blocks of text and headings. However, if your charity's publication only has a few pages, a plain sans-serif font should be fine. Legibility is also affected by other font characteristics, such as x-height and counter size.
Font choice can also impact the perception of your charity's publication. For example, Comic Sans MS wouldn't be suitable for a publication that needs to project a corporate image, but could work in a publication for younger people. Bodoni MT wouldn't be suitable for promoting a state-of-the-art project, but could be used in a publication that aims to evoke nostalgia.
To learn more about fonts, I recommend the book Typosphere: New Fonts to Make You Think. More information about this, and other recommended graphic design books, can be found in the recommended book list.
You may want to choose a couple different fonts for your charity's publication - perhaps one for headings, and another for body text. However, don't use too many fonts, or too many different font sizes, as this will make your design look chaotic.