Overcoming Remote Desktop Limitations

I have a server running server 2003 that hosts quick books. There are two other computers in the office connected through a linksys router-1 wired and 1 wireless. Also a home computer and another laptop with a sprint air card. We connect from home and with the air card laptop using remote desktop. Getting ready to add a couple more air card equipped laptops and am wondering how to overcome the limits imposed by remote desktop when more than two need to connect to the server.