The International Platform on Sport and Development (sportanddev.org) is currently running four online activities to celebrate the international day:
1) Submit your plans: members of the sport and development community are encouraged to share what they are doing and a message for 6 April.
https://www.sportanddev.org/en/news-and-views/international-day-sport-development-and-peace/idsdp-2019/whos-doing-what

2) Publishing articles: opinion pieces and news leading up to the day.
https://www.sportanddev.org/en/news-and-views/international-day-sport-development-and-peace/idsdp-2019/idsdp-2019-comments-news-and
3) Video challenge: members of the sport and development community are submitting videos of themselves saying 'sport is a universal language' in their own languages, along with written comments on the role of sport in addressing the SDGs.
https://www.sportanddev.org/en/article/news/video-challenge-sport-universal-language 
4) Trivia: we are testing our Twitter followers' sport and development trivia knowledge through online polls in the 10 days leading up to 6 April. 
https://twitter.com/sportanddev