I opted my DS out of SRI when he was in public school because I didn't know what was going to get taught by any one volunteer (and having had both an evangelical and Catholic upbringing, I know what kind of random comes out of the evangelicals!!). I started talking to him about how there are people who believe different things around the world, because I knew that my mother would start proselytising to him as soon as she could and wanted him to have a bit of a foundation at home about diversity and respectfully understanding that some people choose stories to understand their world and some people incorporate a bit of both into their world view.
He now goes to a Catholic school since we moved area and that was a conscious decision on my part. I feel far more comfortable with him learning about the Christian God-view of the world in this environment than in the SRI model, and it's a framework I'm very familiar with so I can help him navigate it a lot better. His own teachers are teaching it to him so I can get answers and ask questions directly to someone with a recognised qualification, rather than those volunteers who are not bound by teaching ethics or by any kind of pedagogy outside of their own church's requirements.
I talk to my kids about other religions, and will be making a conscious effort to keep doing this. Not because I believe 'they can choose when they're older', because I'm not raising them to think they even have to have a choice on the radar, but because they will come across people who have all sorts of beliefs and I want them to be understanding and accepting of that (unlike my DP, who is quite intolerant about it).
I had an RE teacher at school (he's now a comic...go figure!) who was happy to tell us that he thought it ok to think of the Bible as allegory, as stories representing knowledge of the world, rather than facts about how the world came to be. I tell my kids that many religions' stories of how the world was made are very similar in theme.
For my own part, I see more value in kids being taught about Aboriginal Dreamtime than be fed Christianity via SRI, in public schools.