He's Catholic. I don't know about her, and I don't think he had his previous marriage annulled, so I don't know if they're planning a religious ceremony or not.
I emphasized that I think the biggest problem is concealing the first wedding, if that's what they do. If they are both religious and would be doing the second ceremony for the religious aspect, I think that's reasonable. But they want to hide the fact that they would already be legally married, and they think their families would be upset about the secret legal ceremony, which I think says a lot about where they and their families are coming from in terms of the legal/religious ceremonies being separate concepts. Which is to say, they aren't.
I'm trying to figure out how to phrase this...I think it's a disingenuous 'out' to say "well, we are having both parts of the marriage ceremony separate and a year apart" if you consider yourself to be fully married and refer to yourselves as husband and wife after the legal ceremony. There are definitely people who do not feel they are married until they have said their vows with their god as witness in the presence of their religious leader. That is not the case here. In any case, if the religious part is important to them for the religious bit, I'm certain that they could have a small religious ceremony on reasonably short notice. They've been engaged for about 8 months now, so it's also not like they couldn't have already been working on this if it were that important to them.
I also think it would be wrong to not have the children at their legal wedding. They should be involved for sure. So I don't think "for the children" is a good reason for a second, large ceremony. If they do anything for the children, it will be to teach them to not deceive.