There are some ways so play Empoleon...
a) with Mantine and Palkia
this is the version I tested a lot, it brings great disruption, exspecially to any Claydol decks. But even with Lapras as starter, its damage output and speed are not high enough to beat G/G in more than 30-40% of the games.
b) with Claydol or any similar support
fastest version, but has no disruption except for Wager + Suppreme Command, which doesn't hurt the current metagame that much, and it also makes far too less damage.
c) straight with Cessation Crystal
hurts most of the decks, but is extremely slow and has no special tricks like the other versions.
But with the new Empoleon that will most likely release in Majestic Dawn, the deck may get a comeback, but unfortunaly, not in time for your Regionals. Empoleon is the absolutely strongest card in the Entry Pack 2008, if the translation is like I think. With damage up to 100, its strong enough to do enough KOs, in addition to that, it can do 30 to 2 Pokémon for 2 energy. So get it out T2/T3, damage their Gardevoir and Gallade for 30, next turn finish them with 100.
I think Empoleon should be taken serious at nationals, maybe it can even be one of the big newcomer decks along with Garchomp variants and Eeveelutions decks.