Sorry Metro. I was in a hurry and managed to overlook your entire post. I know I've read that guide more than once so I can't believe that I missed it.
What's really crazy is that I posted this and then promptly got the option to move River McIrish in. I guess that the conversation needs to be geared in a certain direction though, because as soon as she thought my sim was funny, he could no longer invite her to move in. This has been one of those major frustrations for me, along with BFF.
It's funny, because I thought there was so little that you could do with children...
Oh. Wait a minute. If you can read children's books to children, I'm not getting that option either. I've tried it and then stopped thinking about it. I don't see this answered in any of the guides, but I'm probably either doing something wrong or there's a glitch in my game. It has been glitch-riddled lately