iNaturalist is a free observation platform that acts as a place for people to record biodiversity observations, interact with other enthusiasts, and learn about organisms. Observations from iNaturalist can also contribute to biodiversity science by being shared with open science projects such as the Global Biodiversity Information Facility (GBIF) and the Encyclopedia of Life (EOL). Scientists (and anyone) can freely access and use these data to address their research questions.
Adults can sign up here here and use it with their children.