I'm so sad to hear about your mom. I suspect that your exended family will be a little chilly toward you but I suppose it's nice that they are at least making some sort of accomodation for you and your daughter. It might actually be for the best that you are out in the camper because then you can talk freely with your daughter and on the phone with your friends.
As far as their wanting to witness to you - it's quite possible that they will. Then again, they may not. For me, I think rather than revert to their 'witness speak' by reminding them about spiritual separateness (or whatever the phase is), I think I'd be more inclined to quip back: "Please. I'm not interested in your religion. I'm here because I love my mom and want to help keep her comfortable."
Then again, if saying something like that upsets your mom, then it's not such a good idea afterall.
However it goes, I know that it's an important event in your life. I truly hope that you and she find some nice tender moments and create a few more loving moments for the three of you.
My heart is saddened. I wish you strength, grace and clarity of thought.