If your community produces special publicity mailings for important liturgical holidays, like a mailer or an insert in the weekly bulletin, invite tech-savvy young adults to design and produce them with you. Many of them probably navigate the necessary software with ease!
Facebook, Twitter, and innumerable new technologies may help you promote young adult ministry programs. But do not be confused: there is no more meaningful invitation than a direct, personal invite — even among tech-savvy young adults.