It was a happy day for Yvonne Leung Yin-fong when she volunteered to play with a group of mentally disabled children - and capture the event on camera. 'When I saw the huge smiles on the children's faces, I realised happiness is a very simple thing,' said the 15-year-old from New Territories Heung Yee Kuk Yuen Long District Secondary School after taking part in 'Give a Day, Get a Disney Day'. She added: 'Volunteering for this scheme was worth it - it was a very satisfying experience.' She earned four tickets to Hong Kong Disneyland and won a video competition for her interviews with the children and helpers. If you want to volunteer - and get a free ticket to Disneyland - registration details can be found at www.giveaday.hk .