I would personally suggest client/server for this project. The load should be light enough that one of the machines should be able to host the server while playing the game no problem. The reason I'd pick client/server is the simplicity of the model. Its very easy to keep one consistant game state (i.e. the server) and have it send that state out to the clients. No worries about a client getting out of sync, because it can just get the current state again from the server. I think it's much easier to conceptualize, personally, as well.
Client - > Fire Shot (position, direction, shot type) - >
Server - > Add to list of shots - > Check shots for impacts - > Tell clients that Tank A was hit - >
Client - > Blow up Tank A
Hope that makes sense : ) Take care and good luck!