Here are some useful lists of service projects that even young children can participate in:
A Year's Worth of Monthly Service Projects for Families
12 months of family service projects
It's COOL to Care for Others During Hot Summer Months!
Fishes and Loaves Service Project from Deeper Kidmin - the children prepare meals for families in need of a hand
And a thoughtful blog on Teaching Kids to Love. It is directed to parents, but has some great points that apply in the classroom, too.
"Let your neighbors know that you love them in appropriate ways (aka: don’t be weird). No one likes to be thought of as a project, but everyone wants to be seen, known, loved, and respected. As you look for opportunities to demonstrate genuine and authentic love to others, model these moments for your children. Identify ways your family could show love and care to someone in a way that he or she would feel seen, known, and authentically loved."