I have to write a book for class and I have no idea what to write about it must be kid friendly,appropriate,and godly.

you should make it an adventure so maybe there found clues to something and there trying to find out were it leads to

Not sure how long you have left to write it in now, but what about rewriting a classic, but for children.
So like 'Don Quixote' become 'Jon Coyote'
About a boy diagnosed with terminal cancer who in order to deal with the diagnosis and the treatment retreats into a world of fantasy. He pulls those around him into his make-believe world in particular another small boy who is in the hospital visiting his mother who plays the part of Sancho Panza.

I'm not sure about the 'godly' part though.

you should write about two kids going in the forest and they lost there mom and dad