Dogs looks excellent in capes when they are sitting down or running. When sitting, the cap flows nicely down their back. When running it gives the effect like they are flying. However, if they are standing on all fours, the cape always ends up draping down one side or the other and just looks like a dirty towel falling off of them. Believe me, I'm a cape enthusiast. I've tried it, but it just doesn't look good.
Nothing feels better for a child than wearing a cape. I can see the desire to want to put your best friend in one too. Unfortunately the only fabric kids have at their disposal are blankets and towels. It feels less heroic when your cape has a chocolate milk stain on it, or is freshly wet from a bath.