Heather, have you tried to get them to use a litter box? Bunny should have no problem with it at all since she is older. Older buns are so much easier to train because they've figured out they don't want poop and pee in their food, etc. Even wild bunnies will select one area of burrow as their watercloset.
As I mentioned to Tazz, the key to get them using the litter box is to put some of their timmy hay in at one end in a pile. The other trick is to put the box(es) where THEY want it, not necessarily where you want it. Just put out a pan (or two or three) and see where they go, then if necessary move the pan to where the location they choose. You usually should start out with several pans and then gradually take them away as the buns get used to them. You should also have at least one in each room they have access to as they won't they the living room (especially if they are having fun) to use the litter box by the back door. There's ways to hide the litter box too if you're concerned about appearances..... You might check the house rabbit soc website on litter training. It really is easy! ;)
Try it, you'll like it!