If you're not going to be able to water it for that long. Pull the light up away from the plant so that it still gets light but the heat from the lamp doesn't dry the soil so quick.
This would be my advice. I had a seedling of sour skunk in a cup that went through 1.5 light cycles and the soil just dried up from the heat and wilted to death the seedling. You gotta do your best to conserve the moisture. Do that, and two days won't be two bad. (I know) But if you got more seeds, then eh well.