It's not clear which license I should get.

I have a web design company (http://www.webwalkerdesigns.com),

As I design websites and make them live, I want to give my clients the ability to make changes to their site.
    Each one of my clients have approximately 1-3 people who would need access to make changes to their site. Which license       should I get?

Any help is appreciated, I don't want to pay more for something I dont need.