Have you just tried some disgusting habits to ensure they don't come over. Like pick your nose when they're talking to you, fart loudly and often, draw pictures of hideous scenes of death, read a book with the dumbest/corniest picture of Fabio you've ever seen, cut your toenails on the table they're using to read the bible, seriously put your imagination to work I'm sure you can get some good stuff going to completely mess up their plans. Hey when they ask you questions answer with something stupid.
"Do you even believe in Jehovah's will anymore?"
"Jamaica is nice, well the resort side of Jamaica, obviously not the shanty-filled people stabbing each other side of Jamaica, still it is rather nice and I wouldn't mind going there some time."
"If you could turn with me to John 14:7?"
"Speaking of Turns, did you see 'As The World Turns Today' if you did, don't tell me anything I'm going to be watching right after you guys leave. Unless you guys want to watch it with me."
"Armageddon is just around the corner you know, maybe it's time you start thinking about that?"
"Armageddon is just around the corner, are you kidding, it seems everything is just around the corner. I was watching the news the other day and they were saying that these guys from this web place Myspace hide around corners in order to kill random people from the website. If they came to me I'd have to say "Armageddon outta here" Ha get it? *heavy sigh* ah good times"
Just some suggestions...