There are hundreds of cats round about where I live, and I assume they find their way home for their dinner, and over the years I have had several cats. I have never kept a cat indoors, even letting kittens have the run of the garden
and apart from one getting run over despite living on a very quiet lane they have always come home. You have got to decide whether you want them to live a normal life and let them get on with it, or whether you want to keep them as 'house' cats and never let them out. I know what mine preferred. Going out hunting and playing in the garden is a natural thing. As catlavender said though, don't leave it too late to get them neutered, or you will end up with unwanted kittens before you know it (and then have to find loving homes for them, which as another poster has found out is not so easy).