I believe that the idea of children worshiping only with their parents is not a relative way of worship today. That is that children need to be put in seperated by age groups in order to successfully present the gospel. I also do believe that it is important for children to witness their parents in worship. However, the gospel has change and that is why we need to present it in such a way that we can each understand. The gospel, or "the good news" is no longer about God delivering his children from sinful men in the world, but rather about God delivering his children from their own sin. It has become a spiritual battle and that's what we need to remember.