How do I add satin stitch around applique on kids jeans?

I've gotten pretty good at creating appliques surrounded by satin stitching on my sewing projects, but I've never embellished anything already made. I've seen some amazing appliqued kid's jeans on ebay and I'm ready to give it a try, but I can't imagine how I'll turn and pivot on the leg of jeans. Do I need to rip out a side seam in order to get the jeans moving freely under the machine? And if so, doesn't it show up when you sew them back together? Any suggestions would be appreciated! :)