Show your children multi-media presentations in English. Download TV programs and videos, order DVDs through the Internet, stock up when you return back to your English-speaking country to visits, or ask friends and relatives to bring DVDs when they come to visit you. Not only will your children have the opportunity to improve their English language skills, but these tools will allow them to maintain a connection with many aspects of their American culture.
Read to your children. Bring age-appropriate books with you when you travel to your ministry; you can also order books online. Start a lending library in the community where you live. Encourage other missionary families to work together to operate this library. Other families will be inclined to assist if their goal is to also strengthen their own children's English skills.
Speak English in your home to your children. If your children attend school with non-English speakers they may begin to prefer the dominant language and adopt that language as their preferred native tongue. Continue to maintain English as the primary language in the home. Speak at the level you would use when speaking to a child in an English-speaking country -- don't lower the level of your English just because a second language has become the child's dominant tongue.
Organize hobby clubs with local children, especially children of other English-speaking families. In addition to a club that specifically teaches English-reading and writing skills, you can create hobby clubs that demand that the children read and write English. A stamp club will teach the children to read and acknowledge the stamps of other countries, many of which appear on the stamp in English. Different sports clubs allow children to engage in a healthy physical activity while listening to the instructions and guidance in English. If Christian, engaging your children in English Bible classes, where they can invite their friends, strengthening your ministry.
Hire a tutor. Sometimes parents are unable to teach their own children properly because the parent-child relationship doesn't extend to a teacher-child relationship. If this describes your relationship with your children, bringing a tutor into your home is a solution.