At last I let the cats out. At first I only let Bubbles out so I could watch him and then later I just opened the door so Madness and Mrs. B could also go out. Bubbles and Madness were very excited and I think they climbed every tree in the yard! Mrs. B just sat in the door and watched. They were good kitties and did not go very far and came in by themselves.
I'm so relieved that is went so well. They were supervised and I made sure to talk to them all the time so they could hear where I was. They will only be allowed to go outside when I'm at home and can watch them - that means only on weekends or holidays. It is a big change for them since they were used to going out every day, but I think they will be OK with that.