fanfic help please!!!! (click here if you've seen Hocus Pocus and Avatar: The Last Airbender)

so I want to do a crossover of the show Avatar: The Last Airbender with the movie Hocus Pocus and here's what I got for a cast so far:

Max - Sokka
Dani - Katara and Aang
Allison - Suki
Thackary Bynx - Zuko
Winifred Sanderson - Azula
Sarah Sanderson - Ty Lee
Mary Sanderson - Mai
Ice and Jay - Jet and Freedom Fighters

that's who I've got so far, I need some help thinking up who should play Billy and Emily

any ideas?