@VulkanIt looks like there are two TMs in your CS, but I'll let it go because your avatar and his Pokemon have less than six moves. Or maybe I'm going soft.
I'm going to have to nix the 'transferring life energy to others' part of your legendary powers. Yveltal's powers can only destroy and absorb life energy. It's Xerneas' job to give out life energy.
I'd also like to reduce the range of Alain's life-draining powers to about five meters, and it takes a good deal of time to completely drain someone even with direct contact. I want to make sure people have a fair chance to stop the harrowing powers of death and destruction. Are you okay with these compromises?
Other than that, your CS looks good. As others have said, I like the interesting contrasts between Xerneas and Yveltal and what is expected of their Pokemon.
As for dinner, when you're approved, you can literally just show up. There are pamphlets all over with a schedule that mentions a free avatars' dinner at the Ritzy Raichu, hosted by the mayor. If you decide you have registered as an Avatar earlier that day, you will already have a VIP pass and can get in without question. If you decide you didn't want to register, you'll have prove you're actually an avatar before they'll let you in. I'll let you choose whether or not you officially registered.
@Sickle-cell, I'll give you the same choice. If Tantalus didn't register earlier that day, I'll say Porygon-Z scanned you while shaking your hand.