Marble painting has been used in education for years. When using with your youngest students/children a great way to be sure it remains fun is to control the object you are using for the painting. This can be done in a box, oatmeal container, etc. The problem here is the progress of the painting can not be seen. The understanding of motion is not developed. To support the learning you want from this process use a clear container. Recycling the clear containers that hold fruits, bakery goods or salad greens has worked well for us.
* explore how different shaped objects change what happens, how about the weight, the size, how the container is moved