Your plan of attack sounds good to me. The paper-backed products are perfect for this kind of project. I usually use wonderunder brand, but there's also steam-a-seam, it comes by the yd & in pkgs, depends what your store carries.

Wonderunder comes in lite, regular & heavy weights. Maybe pick up a half yard of reg. and of heavy. Or if the girls' appliques are really lightweight, use the lite variety.
When you fuse them, use a press cloth (scrap of the same fabric would work, cut it a bit bigger than the iron shoe size, or any lightweight clean fabric you have on hand.)

After you've fused it per instructions, let it dry on the ironing board until cool, without moving it or lifting the press cloth. Then, turn it over & do the back side same as front, letting it cool. That extra minute of cooling off really helps set the fusible, IMHO. Good luck with your project, the kids will be flying around in no time!

I would say to also be aware how hot the iron is. Some of the slinky, sparkley, etc fabrics have a lower heat tolerance. Don't want the cape or the designs to melt or distort. So practice on scraps first. This sounds like a cute idea! You should post a picture when you have them finished.

tish

I went to Joanne's and the helpful clerk recommended Heat 'n Bond Ultrahold. I was working on bonding Superhero and Batman emblems together before affixing them to a polyester satiny type of material.

I agree with both of you that using a press cloth is an absolute must when working with meltable fabrics. And the advice to leave it alone to let it cool works best to allow better fusing.

I fused all types of fabrics together with great success and I thank both of you for your helpful suggestions.