I'm using two infra red beams (one at the start line one at the finish) which the r/c car will break through to trigger the starting and stopping of the timer.
How are you detecting the beam break? Are you polling or using interrupts?
Does the board have a clock that can be used?
Yes. Both millis() and micros() return the current time (one in milliseconds, the other in microseconds). Record the time the first beam breaks, and the time the second beam breaks. The difference is the time down the track.
Also can the board be used to time two seperate lanes at the same time.
Depends on whether you are polling or using interrupts. With polling, yes, but there are only two external interrupts available, on pins 2 and 3.