Someone please do a brief demo of how multiplayer could work. (Could be like a chat group)

Check out the instructions for wireless communication. http://smilebasic.com/en/reference/#wireless You'd first want to connect with MPSTART from both devices, then you can easily transmit data using MPRECV and MPSEND. They're pretty straightforwards in how they work.

Do you have two 3ds' and two copies of SmileBASIC to try it with?