There are a lot of timers available that you could use, both 115v and 12v, that can be very easily programmed to come on so that they have enough light to draw them into the coop, and then turn off for the night, for as little as 10$ - 15$. Once they are in they don't need light all night. Since they are young you may have to physically put them on the roosts each night until they figure it out. Sometimes it can take a while, what ever is habit for them becomes 'normal', you need to make a new habit. My roosts are also 2x4 or 2x3 wide side up.