It's important that everyone feel a sense of ownership in the project. Ask for suggestions or creative input into the project. Give them some space. What a treat that would be. Every project must have a deadline.
Deadlines are as important as communicating clear objectives.
Dates and times should be specific, strict and realistic. Intermediate deadlines will help avoid last-minute producers. Without deadlines, your volunteers might not feel responsible for completing the task. Projects with a deadline will almost always seem more important than those without. Having a communications and reporting system in place will eliminate unnecessary feedback.