Advice on letting cat outside.?

I have two indoor cats. But one absolutely loves getting out in the back yard, and she thanks me profusely with meows when she's out there. I adopted her as a young adult, so I ume she was used to being out before. The good thing is that she stays within a 100 foot radius and doesn't seem eager to venture off. Would she likely start exploring if she got out more? I wouldn't want her doing this both for her safety and consideration of neighbors. I'm not a proponent of having outdoor cats, but given her fondness for it and so far her willingness to stay in the yard, I'd like to give her some time out there as long as she doesn't wander. Any suggestions?