I really think the only way you can tell if a particular cat will be friendly is to interact with him/her. After all, Maine Coons are usually very friendly, but so are Ragdolls. You have your Ragdoll who doesn't fit the stereotype, and my brother has a Maine Coon mix (giant guy, lovely, etc.) whom I have never seen in person. He's friendly to my brother and his wife, but no one else. You might think there was no big yellow cat living there were it not for the tell-tale long yellow cat fur lying about - their other two cats, whom I HAVE met, are black, and black and white, so I know Pippin exists!

Back to the subject, play with the kitten, see how he reacts to other cats, how he reacts to you, your daughter, etc. It's the only real way to tell, I think.