How up-front about not being religious should we be?

I was recently at some friends house in Iowa (I live in Colorado) with my children. These friends happen to be extremely religious and my children and I aren't at all.
Through most of my life, I have tried to be very tolerant and respectful of other's beliefs and opinions. In this case, that meant at dinner, when they prayed, I would stay quiet, though not participate.

This year however, they went to hold hands prior to the prayer. I didn't think much of it and just held hands with the two people on either side of me. But, I noticed my oldest two children refused to do so and one of them gave me an odd look for the fact that I was doing it.

It made me ponder just how tolerant I should be. I've been getting less so because of the changing tide in this country, especially with the Bush Administration. But, with friends. I also noted on this trip that they were willing to give me a book on Christianity that I'm sure they hope will convert me, but I'd be uncomfortable giving them a book trying to break them of their faith.

This is certainly something each of us has to ask ourselves and for me, I've been making a concerted effort to be more upfront about me beliefs, but I also don't see a lot of gain in being argumentative just to argue or with people that aren't really open to it. I tend to be much more willing to let them know what I think without being pushy about it and while being willing to listen to them.