Find pics of actual children and draw them. Seriously, it's that easy. Or just reference the pics. Your piece needs other work, but you asked about the kids and I'm half awake.How in the world do I draw kids, aka people who are not 20s to 30s? My figure drawing texts in regards to anatomy help with the older side, but very little consideration is given to teens and younger.
I was commissioned for a piece of merchildren, so I'll post progress pics to continue to ask for help, but I don't even know where to start for kids. In the past they always come out as looking like mini-adults. I know the problem area is the face proportions and features like that, as I think I have the body proportions okay.
Here's a piece I did about a year ago. I've progressed in regards to the faces for the woman and man (just see my avatar!) so I'd like more focus be given to the two kids. Of course, any necessary criticism is welcome; that's just where I'd like the focus to be.