Be careful with corn cob bedding. It may work, but I've heard that it can cause impaction if the mice eat it. Think of it this way. What are mice known to eat, besides cheese
,....corn! if they eat that bedding, I'm not too sure it would be good for them. Also, I've heard that it gets moldy fast. I actually use a product call SoftSorb and its awesome when mixed with baking soda and rabbit food pellets. It is a bit more expensive than aspen, but I hardly have any smell issues with it. I'd check it out if I were you. Its just one of those things. If you had a huge rack full of mice, it could get expensive, but if you only have 2 groups, then its great.