You thought incorrectly.
If you fail to declare your second child and boyfriend now - you will NEVER be able to bring them to Canada.
Also, if IRCC finds out that you failed to declare a child and common law partner, they may revoke your PR status and the PR status of your son - and order you to leave Canada.
There is nothing to be torn about. Again, you have no option but to fix this problem now. Once you land in Canada and become a PR, it will be too late to fix this and the damage to your life will be permanent.