The backyard is completely fenced and I leave Darby outside with Edward (Darby stays outside the pen). Darby is super gentle, but will alert me if any other animal i.e. cat were nearby.
Darby has adopted the buns for his very own. He goes to check on them every morning and evening. Sometimes he just lays outside Edward's cage and watches rabbit TV.
Both of the bunnies used their litter pans and were very clean. It has been good for them to run around a bit, but warmer weather is on the way. It may be awhile before they can go back outside.