I have a small business too and I use Wrike to manage it. I'm a huge GTD fan, like most of us here and I started to use Wrike for organizing my personal life at first. Then I realized that the application gives me more than just a to-do list. Now I run all of the departments in my small company in Wrike. And it really works! My staff say that they like it, cause it's easy to use. I feel that they became more productive. I recommend you check this tool out. It might be a good solution for you too.