I designed the board with 3-pin male headers (signal, VCC, GND), with the signals connecting to the ADC pins. I plan on using this board for other projects as well, so I wanted some flexibility in the sensors I choose (hence the pins that let me plug in said sensors). I made the custom PCB because I don't like the idea of shields much. They're great for prototyping, but not for standalone projects IMHO. Also, who doesn't like the feeling of pride when you design something yourself :)! Got it done pretty cheap as well, $35 for 10 boards with solder mask and silkscreen.
What I meant to say was the white edge of the ring! The ring is a black circle (150cm diameter), with a white boundary (5cm thick I think) painted around the circumference so your robot can sense if it's going to fall off! The goal of the competition is to push the opponent out of the ring, and you can't have your own 'bot jumping off on its own, can you?
About the motors, what I mean is that can motors that only draw up to 2A supply enough torque, and at a reasonable rpm, to be of any use? This might sound like a noobish question, but I'm doing this for a high school project, and don't have much experience in this field! Of course, I'm expecting to get thrashed (gonna be up against some hardened college students), but I figured, why not give it a go :D?