This is one of those slightly touchy subjects for people. Sadly, people from all ends of the spectrum have some rather heartfelt, and damn near immovable, ideas regarding children and religion from when it should be introduced, if it should, and of course which one.
This isn't a post about that, really.
Instead this is more dealing with what happens when you have two different religions and two very different cultural approaches to it. Now I wasn't exactly raised Christian, but I did join my local Presbyterian church, eventually becoming an elder when I was in junior high/high school. Although it has been some time since I was last at service (It should be noted that nearest Presbyterian church is somewhere in Tokyo), I still consider myself to be Christian and Presbyterian.
Beloved is nominally Buddhist, though she isn't interested in going to the local temples or having a butsudan, a Buddhist altar, in the house.
The both of us decided from day one that while our faiths are different, that shouldn't matter in terms of our marriage and any children we have would be allowed to find their own path. Neither one of us would, therefore, force our children into any religious systems, settings, etc., nor would we teach about our respective faiths until they were old enough to ask about it themselves. As with many things in our marriage and parenting style, the watchwords were compromise and communication in order to lesson the shocks and bumps from two different points of few and cultures and keeping them from wrecking our relationship.
What became very quickly apparent though was that, while this was a great idea, really, Japan and the US have a very different approach to the very concept of religion. There's an old joke about Japan, in runs thus: If you ask the Japanese about their religious beliefs, 78% will claim to be Shinto, 78% will claim to be Buddhist, and 78% will claim to not believe in anything at all. An actual Japanese saying relates that one should be Shinto for birth, Christian for marriage, and Buddhist for death following the customs of going to a Shinto shrine with a new baby, a church for your wedding, and after your death, your relatives will invite a Buddhist temple to help send you to your next life.
In between those times, most Japanese don't consider themselves particularly religious except... Except that there are loads of cultural events that they do that involves various religions. Families will go to shrines and temples for New Year's, the big holiday in Japan. Children will walk to school carrying a charm purchased from a shrine or temple to keep them safe, students who have a test will not think twice about stopping at a Shinto shrine and writing a prayer tablet asking for help in their studies. There are a host of other events from local festivals centered around the local shrines or temples to national holidays where people return back to their hometowns and attend to some religious obligations, all the while claiming that they are not doing this due to belief, but because they are Japanese.
This was the biggest hurdle that I had to get my mind around as a father when these various events started to pop-up. Americans of course are more used to the wall of separation between Church and whatever. THIS is a religious thing so do this because we believe. THAT is not. THIS and THAT shall not mix, doing so would be somehow wrong. The idea of doing something religious not because you are religious, but because you happen to be American is... off somehow.
This is not the same as, say, Christmas being celebrated by people of different faiths, or no faith at all, but more akin to the notion of, for example, a family of American atheists going to Christmas service and receiving Communion because that's what one should do as an American during Christmas time.
But for the Japanese, there's no particular problem with having a full Shinto blessing at the birth of your child and having that child's name recorded as belonging to that shrine, even if you don't happen to believe in Shintoism and have no plans to visit that shrine again.
Things that I would view as a violation of our agreement, for example Beloved making arrangements for the boys to be taken to a local shrine for a blessing, was explained as "This is what we do as Japanese" by Beloved. I admit that the first time, sitting in the shrine while the priest chanted Makoto's name to the kami, I was a bit perturbed. It seemed very much like a baptism and there was a few times when I almost wanted to ask Beloved just what we were doing. The same with Beloved's parents teaching Makoto how to present rice to the household kami at their house (The proper way to do this, by the way, when you're a child is to put the bowl of rice into the tokonoma, bow, fold your hands together, and mumble "Ma ma ma ma ma ma ma ma").
But getting back to the watchwords, I talked with Beloved instead of charging in like a bull moose with a thorn in his butt. The more we talked, the more it did become apparent that these rituals, which to me seemed very religious, were very much cultural and done more because Beloved wanted her sons to grow up like normal Japanese boys.
The more I thought about it, the more I have come to appreciate the Japanese point of view, it seems a bit healthier than the near obsession that many Americans, again on both sides, place on religion and trying to include it, or restrict it, from their lives. Besides, we also compromised a bit. While I'm still not telling the boys Bible stories or taking them to church, there's nothing that says while they celebrate New Year's with a shrine visit, a week before they celebrated Christmas, American style.