Maybe it was a son of a Apollo thing, but whenever Will slept at night, he slept like a rock but as soon as the sun started rising, he was up and awake and ready for the day. As such, he was completely oblivious to the world and what Nico shouted at him (to which he would pout if he had heard). However, a thorough kiss was definitely a surefire way to wake him and well, if Vex wanted to come be a part of the wake up process, Will wouldn't complain.