Study some examples of epic poetry with the children. Rather than asking them to read the "Iliad" or "Beowulf" from start to finish, concentrate first on explaining the rich and colorful stories. For example, have the class act out particularly dramatic sequences using modern language.
Take some short extracts from the text you are studying (a dozen or so lines), and invite the children to comment on features such as meter, rhyme, imagery, voice and so forth. Teach the children about different types of meter and foot, painting these conventions as tools, rather than rules. Remember to focus on what is so effective about the poetry; your enthusiasm will rub off on the children.
Start slowly. To begin with, encourage the children to write a brief story about some adventure from their own lives, in straight prose. They should concentrate on making it as dramatic and, if possible, as heroic as they can. The focus at this stage is to achieve the right narrative and emotional style.
Set the children the task of converting their prose adventure into a fully fledged epic poem. They should be short, but intense. Encourage dramatization and romanticism. Suggest that the children focus on language (imagery, alliteration, etc.) as much as they focus on meter and rhyme as a means to their end of creating an exciting, dramatic tale.
Invite the children to read their poems out loud in front of the class. After each reading, the class should discuss the good and bad qualities of the poem. This is an extremely important part of the learning process, as every comment the children make or hear adds something to their understanding of what makes a good epic poem.
Invite, but do not demand, further submissions. If a member of the class has particularly enjoyed the project, he or she will relish the opportunity to present another piece of work in the same genre for your perusal. Enthusiasm of any kind should be nurtured.