I wouldn't want to let them out to run around like that either, they can find ways to get loose and never be found.
What I did though, was I made a very large pen with a shallow pool they could get in and out of on their own, half in sun, half in shade, they could run about in the grass for about ten feet not including the pool if they wanted to.
By the way, did you ever get them checked out for any illnesses or parasites? I know you were having trouble with Yugioh before.
Turning on the Aquarium lamp in the morning is MY cup of coffee.