Well, the atom processor is designed for small devices like netbooks. The processing power of this processor is even slower than centrino processor.
You said that you will have 3 people using it, but you did not say how will they be using it. If it will be used as a file server only, than you should be fine. If you want to use more options like mail, vpn, or any SQL intensive applications, I see no reason why it would not work, but it will be Slow.