Perhaps start with a short term project, for example, with the women at the local county jail just before Christmas or Mother's Day. You will need supplies. Gathering the books and tapes you need is a wonderful chance for the general public to begin to be aware that there are many children who have parents in prison. They need to be new books since these are the only gifts children will receive from their mom, and they must be light enough to mail. Women's groups, fraternal organizations, the older children in schools or church groups, and school groups may be encouraged to donate them.
Many books are appropriate for all children.
Dr. Seuss books and The Little Engine That Could are examples. However, since most of the children of imprisoned parents live in poverty, it is important to avoid books that are focused on middle-class suburban stories. Now days there are excellent multicultural books that parents would be delighted to read to their children. Children who donate books should be encouraged to find books that they would enjoy themselves. The can often get them from book clubs at school.