You start with people who excel!!
Missions is easy- Wycliffe, New Tribes, Child Evangelism Fellowship, Slavic Gospel, and some denominations like Southern Baptist... (links below)
But your baseline examples would be found in the Bible-- which characters in God's book exemplify service, missions, and sharing the gospel sacrificially? Who teaches us to appreciate each person and their unique design? The answers are found in the Bible...
start with the Tower of Babel, look at Ruth and her sacrificial story, Queen Esther, King David, Daniel and his life, Joseph, Abraham, Moses, Jesus, John, Disciples, Saul/Paul, Simon, Priscilla/Aquila, parables, Mary/Martha, Great Commission, the fruits of the Spirit, Christian Living...
It's our call to Know, Love and Serve the Lord Our God with our hearts, souls, and minds, and love our neighbors (both here and abroad!)...
Then work to help your children look at life beyond their own home and experiences, it's a big challenge to even get young adults to stop thinking about me/self, and be ready to think about others. Spend time helping others- serve at a food bank/pantry, help the homeless, help refuges, help missionaries: send them mac and cheese/choc chips, and whatever else they can't find, make calendars to send overseas, purchase trade products made by women hoping to support their families, mission trips, pray for missionaries, write/email missionaries, expand their horizons... help them see the WHOLE world. Skype with a missionary. Host an international dinner and have foods and customs from another person, invite college students over from a local school that are from overseas, just look around you and be intentional!
A favorite book to teach kids that people exist beyond their comfort zone is
Window to the World
Missions materials are all over the place. The best way to help children learn to serve, to lead and to give sacrificially is through role models. So missionary visits when they are home on furlough are helpful, as well as local adults/teens who serve right where they are, visiting and sharing a story or testimony can be a bigger motivator than any curriculum on serving God. But there are some great tools out there for direct skill teaching and even role playing or simulations! Here are some I am aware of, this is just a few!
- New Tribes Mission have Children's Resources Some are free, most are purchased.
- Wycliffe Translators Kids Resources Many are free downloads, but can also be purchased, and they have picture books and curriculum guides as well. Fact pages, games, centers, and lessons! They even teach kids about Bible translation.
- Recommended by Wycliffe (List)
- Akebu to Zapotec a book of Bibleless people
- CEF (Child Evangelism Fellowship) has stories of famous missionaries and also christian life/ doctrinal materials.
- Southern Baptist has a blog, and resource directory. Haven't fully explored it, but I will some day!
- Slavic Gospel Association has a free mission kit. The lessons are engaging and teach different dimensions of service.
- Public Schools use materials from Free Spirit Publications for social and emotional needs. They have some great ideas of what kids can do as service at different ages/stages in their materials which many public libraries have.