I prefer to double bat. It gives great definition to the quilting. I have done it with double wool, wool over cotton, wool over 80/20 and also have used Hobbs Polydown in place of the wool for all of these combinations. In your case I think I would go for wool over cotton or two layers of cotton.
Here are examples of wall hangings I have done this with:
Double wool
http://www.quiltingboard.com/picture...c-t265846.html
double cotton
http://www.quiltingboard.com/picture...s-t278354.html
Wool over 80/20 PLUS trapunto work done with W&N
http://www.quiltingboard.com/picture...g-t256886.html
Wool over cotton
http://www.quiltingboard.com/picture...c-t260633.html