When I was in high school, our youth group always held meetings on Sunday evenings. I thought it was a great way of keeping the Lord’s day holy for us kids- we started the morning with Mass, then ended the day with a gathering of prayer, discussion, and fun (sometimes even the sacrament of Penance when one of the priests would visit).
Think of it this way: would you rather have your kids participating in a Catholic youth activity, or at home watching “Desperate Housewives” or whatever other junk is on Sunday TV?