Online learning activities between grandparents and grandchildren are a promising solution for those, who live geographically separated or cannot meet face-to-face. Up to now, little is known about the characteristics these activities should have. In order to find out about the challenges that arise when designing an intergenerational online learning activity we analyzed children's preferences and needs, as well as those of grandparents. Investigating both perspectives ensures that the children benefit best from the activity itself and their grandparents' support. As the identified challenges mainly refer to the general set-up of learning activities, we also discuss a design concept illustrating how to meet the challenges.