Whether deciding to give up ice cream or special treats for a month, foregoing video rentals for a period of time or even fasting a meal, the team effort will make the giving special. Keep track of the money saved, and designate it to a specific mission project. Full of activities, stories, and games for teaching hands-on lessons about money to kids aged 7 to 12. Start with worship. Lots of children's church programs already emphasize worship through singing and prayer, but worshipful giving also needs to be included in the mix.
Children are concrete thinkers, so select mission projects they can clearly relate to.
It's also important for children to give to other children. Knowing what happens with the money helps kids experience being used of God and will motivate them to give more and regularly. Many years ago I was in charge of the giving project for our church's summer Vacation Bible School. We had a Hawaiian theme, and I was able to find a ministry reaching children in the outer Hawaiian islands. The kids were excited.