Actually, it's not necessary to change your font because visually impaired people have the ability to adjust font sizes within their own browser. Specifying fonts like you have can interfere with a visually impaired person's browser settings or special reader software. Take a look at the AARP website for ideas on easily readable fonts for older people.
The reason for the large font is so that older people with failing vision can read it. It appears obvious that web page developers are young males who do the band-eating development on wide screen... more