Have you seen the large enclosure that Tubby & Peanut's Mom has? It is huge and wonderful! It even has room for a catnip plant out there. The top has a cover so they are safe inside yet it is like being outside with the fresh air and sunshine. This might be a possibility for you! I bet Cubby would love it

In looking at it, I had even wondered if it would be possible to build a tunnel from the house and add a catflap that would allow them access on their own - a door that could be locked at night or other times when you want control of them. We use a catflap to control access to our enclosed porch. Our cats go out there and *think& they are outside as it is screend floor to ceiling on three sides.