These are a great water based pen that can be used with your projects. I like Tombow because they are easy for my Kids to use and not too expensive of a choice compared to my artist grade alcohol markers.
I always tend to gravitate towards the primary color sets when starting out. I like to teach our kids about the color wheel and how colors affect each-other. Starting them with the basic primary colors has been a great way to get them thinking about the relationships colors have with together. This pen set also comes with a blender pen for those who like to get more artistic and accurate with their illustrations and colorations.