Your comment about this stuck in my mind all day. I was looking forward to getting back and asking...if you happen to know the answer.
What do they think the Holy Spirit is if they don't believe in the Trinity? I know you said that some don't believe in the deity of Christ...that alone messes up the Trinity for sure.
I was so impressed with our vacation bible school curriculum this year. It was teaching about the Trinity and about false gods. How deep is that? It was awesome to see little children get it so well, yet adults many times do not.