Could you possibly do a 'modified' number 2? Meaning, put yourself out there to them, so to speak, but do it in a calm and non-judgemental way. Tell them that you are happy that they have found someone who brings God alive to them, who can mentor them in their faith, but you don't have the same beliefs and you aren't ready or able to explore the possibility of having that in your life right now. Let them know that because you aren't at that point in your life, it makes you uncomfortable, and while you understand it is their house and you respect that, could they please respect that it makes you uncomfortable. Maybe tell them you don't want them to stop expressing their joy and comfort in God, but to be mindful of when you are around and in turn you will agree to be mindful of their enthusiasm and try not to get upset. Possible? I hope so.

My ex-father-in-law became very into the religious life right around the time my ex-husband and I got married. He grew his beard super long and mangy because he said Jesus told him to do it. He and S got in a huge arguement because S wanted him to trim it and comb it for our wedding and he said no, that Jesus hadn't told him to do it yet. Finally S decided it was more important to have him there regardless of how he looked than to not have him there at all. My point is that you may have to find a compromise, but you can't do it by keeping things in and letting it eat at you, and you can't do it if both parties won't talk. I wish you luck with this!