Beginer to arduino looking for suggestions

I have always been a tinerker at heart, however I recently found the arduino boards and have been trying to come up with a project for one since. One of my local r/c clubs is getting ready to start drag racing and I thought this would be a pretty good time to play with one of the boards to create a timing system. For starters, it will simply light up an led in one lane to show who wins, however I eventually would like to interface it with a pc to get reaction times and the times as it goes down the track.

Here is my plan.
The christmas tree (staging/starting light), I had planed on using a separate board for, I will have two sets of sensors for each lane, one to tell when the car is staged and another to tell if the car jumps the start. The board will need to tell when both cars are staged tell the christmas tree when to light up which light, and tell if a car false starts.

Another board will be used to track the timing, I had planned on interfacing it with the christmas tree to the green and red lights to determine if someone false starts or if its ok to start timing when they reach the first sensor (also the second sensor for the christmas tree). I will then have a last set of sensors at the end of the track for the finish line with two leds, who ever wins, that lanes led will light up to let everyone know.

Now here are my concerns.
Originally I was planning on using a break beam ir system, however being around the paintball world had me worried that there might be to much light to use this (it will be indoors under florescent lights). However I havnt had any experience with ir leds outside of the paintball world. Do you think it would work, or should I try a different sensor type. Also, would all of this be possible with one arduino board, or would I need two separate boards as I originally planned. Do you for see any other problems that I have over looked with interfacing the board to the sensors or light tree?

I have found success using the ping ultrasonic sensor, which is pretty accurate, You could use a laser and LDR setup which might be even faster. If you need more information just coment.