[Al3+]

Range finders are a good idea, but they're kind of limited. Unless you plan to have a whole row of them, you probably need a better way to distinguish between gamepieces, robots, and obstacles.

I imagine a possible "find gamepiece" routine going something like this:
Use the camera to find the nearest blob matching certain parameters (depending on gamepiece). If one exists, compute the angle from the x-position in the image, rotate the bot to that angle using gyro, confirm that the gamepiece is still there, then use a rangefinder on the front of the robot to find the distance and drive up to it. If none are found, rotate 30 degrees or so and try again.