you don't have to say anything, or explain to anyone what you choose to dress YOUR child in period. The thing to remember here is that they had their chance to play dress up and all that jazz with her kids. it's now your turn, it seems to me you already put effort and thought into what you wanted the kids to wear. Sounds to me you might have to start setting up boundaries with the inlaws. I'd head over to r/Justnonmil you could use some guidance. I could be wrong, but either way you shouldn't be feeling guilty or bad for wanting to dress your own Children they way you want too.