"There's two goals you want to balance. You don't want to damage your children, and they take precedence. But if you can, it would be better to not alienate your brother. Suprisingly often, it is the loving Christian sibling or friend that helps bring back someone like your brother.
"If it were just your 18-year-old, I'd say go. He sounds like he's strong enough to stand with you. But the younger ones are the wild-cards."
First, I also have a daughter who is twelve and twins that are eight -and they all have a fairly solid grounding in Christianity. However, what they don't have is a fairly solid grounding in the ways of the world. Interestingly, it is particularly my twelve year old daughter I am worried about. She is very innocent and we have kept her fairly sheltered. In some ways, I fear it would crush her if she knew what was going on with her uncle.
Also, try to understand it is not her brother who is now making a big deal of this -at least according to her mother and father. Rather, it is her mom and dad, (and, I suspect, particularly her mother) who is pushing the issue. And, frankly, I don't know why?
I have a girl of the same age and level of innocence, so I will venture an opinion on this.
I personally would not hide my daughter from the uncle. She's eventually going to find out anyway, and (because he's probably a lot of fun to be around) she's going to think you're being unfair to him. Again -- you end up on the losing side.
What you really need to teach your daughter is the truth: that the uncle's situation is, above all, very sad. He's living a disordered, empty, and very dangerous life. She should love him and pity him, and pray that he gets better. She should not be taught to fear him, because you'll lose her on that.
You needn't go into the details of what he does -- she'll find those out on her own at some point, and when she does, she'll be well equipped to understand why his sexual choices are empty and wrong.
You need to talk to your 12 year old. She's probably not as innocent as you think. Sheltering and being honest are two different things. My 17 year old daughter is "sheltered" but we discuss EVERYTHING.
If I stopped attending family functions because of "sinners", we wouldn't have a family anymore.
Innocence is the greatest gift you can give your child. Don't let ANYONE rob her of it! And don't let ANYONE tell you that you are wrong for trying to preserve her innocence as long as humanly possible.
In some ways, I fear it would crush her if she knew what was going on with her uncle.
Then you have a duty in the eyes of God to protect her innocence and protect her from this knowledge. If a family gathering with the brother and his homosexual lover in ANY ways threatens her innocence, there is no more room for dabate on the subject, is there?