Grandmother's and grandfather

Alyson

So I am planning on having my grandmother and my FH grandmother be my flower girls and my grandfather be my ring bearer because I don't have little kids to do it and because I want to include them and have them apart of our big day. My question is does this sound completely crazy? Also what should the grandmas wear? Something to match my colors? Or just like black dresses? Do they need to match each other?