When working on children books I work in a few stages - rough sketch so the client can approve placements and poses, a clean sketch - this one, so the client can approve the details of the figures and items, and then a colored version. Depending on if it's a vector or a raster drawing I also add another stage for flat colors.
This ensures a quick turnaround since edits can be made at each stage and they're easier to apply early on than after the final image is finished with color and shading.