The agency secured the business following a multi-agency pitch.
Exposure was briefed to develop a creative platform that will support Save the Children's global campaign to get 10m people to take action against child suffering by 2010.
The agency answered the brief by exploring the "take action" premise. Central to their proposal is an experiential strategy that will target festival goers and ask them to raise a hand in support of the campaign.
The charity is looking to Save the Children ambassador Gwyneth Paltrow to support the activities and hopes to approach the government at the G8 summit, at the end of the festival season.
Save the children brand manager Rebecca Walton said: "Exposure has captured what our brand is about.
"They have managed to deliver a truly ambitious and creative concept which will engage festival goers and secure new supporters for Save the Children."
Tanya Weller, group account director at Exposure, said: "In today's competitive climate it is more important than ever for charities to engage with supporters using clear, simple and powerful messaging."
The activity will run at family-based festivals including Bestival and the Bristol Balloon festival from May to September 2009.