You can change the font size by adding .tag, .entry-management-links, .entry-interaction-links{font-size: 80%;} to your custom style sheet (http://www.dreamwidth.org/customize/options?group=customcss)

If you don't like 80% as font size, you can make it smaller/larger, or use em or px instead.

Also, any style-related questions can be asked over at style_system