Information technology can serve as a powerful tool for promoting children's learning. In this context, digital, symbolic rewards are frequently employed to enhance task performance. However, it has been observed that once rewards are removed, intrinsic motivation to perform a task may decrease below baseline levels, a phenomenon referred to as motivation crowding. There is a lack of consensus among researchers under which circumstances motivation crowding happens among children. Here, a field experiment with three distinct groups tests the presence or absence of motivation crowding. This paper reports the findings from the cluster randomized field study that investigated a digital health intervention guiding and rewarding children to engage in everyday health behaviors. Behavioral data from 254 children between the ages of three and six was collected over a five-week period. The results provide empirical evidence that digital rewards successfully helped children adapt everyday health behaviors and refute motivation crowding among children in the context of digital rewards. The findings are important for advancing the use of motivation crowding theory in children, for providing insights into children's behavior, and helping researchers develop digital motivational cues for children. At the same time, the digital intervention outlined in the paper embodies an effective and scalable measure for engaging children in health prevention behavior.