ah right yea the green house should be good to work with. Even better if you can heat it to optimum growing temps.
The extra light will help, but of course auto flowering stains will flower no matter how much light they are subjected to. If you plant in May or June I think a "small light" would maybe be alittle pointless but could only help of course.
Remember to tell your friend that yeild of LR (if thats what he's growing) is very much dependant on the pot size aswell as light hours.