Games are important because they help kids get to know each other, building relationships and trust. If you're having trouble finding games, here are a few online sources:
Youth Group Games
Great Group Games
The Source for Youth Ministry
Ultimate Camp Resource
Don't forget that there is almost always one (or two) who don't want to participate. They may not say it but it's probably because they don't feel a part of the group or have some fear of looking foolish. It's always best if one of the kids, and not an adult, encourages them to participate.