Icons should use private use area, not actual characters
As these are icons and it's a font, I'd suggest using the private use area of Unicode that's set aside for cases like this, rather than actual characters such as 'A' etc.

The reason being, even though they look like icons to people viewing the web page, it's still going to get picked up by computers (search engines, screen-readers) as characters.

Source: http://en.wikipedia.org/wiki/Private_Use_(Unicode)
