Otis' Friends

Found here

Last night I heard a hiss and a rattle, and looked up from the kitchen table to see Otis hanging on the screen door, about three feet off the ground. Shocked, I went over to the door and looked out myself. There sat two stray cats on the mat outside the door. They are both grey and white, both looked hungrily in the door. Actually, I think they're feral cats as I've seen them in the yard on several occasions and I've taken to feeding them every night in a little saucer on the back porch. One of them jumped up on my lap, purring and begging for a scratch under the chin. The other is a bit wary and stood off a distance. But there they were.
I don't know what to do about these cats. One of them appears to be a good candidate for being inside with us. But they're a team, those two. Probably siblings. Should I take them to the humane society in the hope that someone will adopt them? I think Otis will miss out on the entertainment value of having his friends come calling if I do that. And I will miss these little furry visitors. What to do?