Even if your wife never manages to forgive you for what happened, I think there might be a much stronger chance than you might realize that you eventually have a much more meaningful relationship with your son by being your true self with him. He's young enough that in a lot of ways, the version of you he loves might not really be based that much on the construction you describe as much as the fact that he knows you love him and the experiences you share (and will hopefully continue to share) together. I think it's more likely that continuing to repress how you feel for years to come will take an emotional toll on you that makes it harder to be able to truly emotionally connect with him at the level you'd like than the fallout of revealing the truth sooner.
For what it's worth, you also may be surprised about how willing even your wife is to accept this. I obviously don't know anything about your situation, and there's any number of things that can influence how loved ones react to something like this, but I have direct knowledge of a situation fairly similar to yours that turned out quite well; my aunt on my father's side has only one child, a daughter from her first husband, who ended up coming out as gay at some point when my cousin was fairly young. They divorced, and from what I'm aware of, continued to co-parent civilly, and my cousin would spent time with each of them during holidays (e.g. she's always spent Christmas Eve with my aunt and our grandparents and Christmas Day with her father). Almost thirty years later, both my aunt and uncle have been remarried happily for years, and nobody cares that my uncle happens to be gay. If anything, I have to assume that literally everyone is much happier in the current situation than they would be if things had gone differently and he had never come out. I don't pretend that any of us can know how things will turn out for you and your family whichever path you choose, but I truly think that if you decide to tell the truth, you'll be giving all three of you the best chance at happiness in the long run.
For what it's worth, you also may be surprised about how willing even your wife is to accept this. I obviously don't know anything about your situation, and there's any number of things that can influence how loved ones react to something like this, but I have direct knowledge of a situation fairly similar to yours that turned out quite well; my aunt on my father's side has only one child, a daughter from her first husband, who ended up coming out as gay at some point when my cousin was fairly young. They divorced, and from what I'm aware of, continued to co-parent civilly, and my cousin would spent time with each of them during holidays (e.g. she's always spent Christmas Eve with my aunt and our grandparents and Christmas Day with her father). Almost thirty years later, both my aunt and uncle have been remarried happily for years, and nobody cares that my uncle happens to be gay. If anything, I have to assume that literally everyone is much happier in the current situation than they would be if things had gone differently and he had never come out. I don't pretend that any of us can know how things will turn out for you and your family whichever path you choose, but I truly think that if you decide to tell the truth, you'll be giving all three of you the best chance at happiness in the long run.