Have business cards printed up for your youth church/group. Then go to a local mall or hang out and give them out having your kids invite other youth to attend your service(s). After they get used to approaching strangers teach them how to witness and use the invitation as an ice breaker with the youth.
We have been doing this for about a year and have led over 50 youth to the Lord. Definitely use them before your next “big event.” Your youth can give them out to friends with the date and time and they can reach you (youth pastor) for info if needed.