I am sharing this on behalf of Dad4Kids. For grandparents looking for something to do together with a young child, our games for preschoolers page includes letter sounds, counting and picture puzzles. The games are in English, so that may matter for a Dutch-speaking child.
An adult can sit beside the child and talk through a task rather than leave them alone with the screen. The page suggests short sessions of ten to fifteen minutes. This is a learning activity for children, not a treatment or a rehabilitation exercise.
What small activities do you enjoy sharing with your grandchildren?