For younger children, it may be best to explain what happened in Japan, but reassure them that they are safe. With middle school kids though, it is a great opportunity for them to learn how they can get involved in charity to provide assistance to those in Japan affected by the earthquake and tsunami. Having them do extra chores to earn money to donate is a start. An easy way for tweens and teen to donate $10 via their mobile phone is by texting "red cross" to 90999.
Beyond this, you can help your older children participate in fundraising events with local chapters of charities. Often times, these may be car washes, walks or raffles for charity. This may even help your child gain an interest in volunteering regularly. In addition to instilling great values, such as humility, older children can learn leadership skills and how to work as part of a team to achieve a goal. It's also a great opportunity to spend time volunteering together as a family. I've done this with my son, volunteering for local food banks as well as the United Way.