Let me suggest that you're overweighing the long-term effects on your happiness of learning something painful (see Dan Gilbert's Stumbling on Happiness for research on that), and underweighing (in fact neglecting) the benefits that would result from knowing the truth.

For instance, learning the truth has placed you in a situation of greater autonomy with respect to your child: you have a greater degree of control over the moment when he/she will learn that truth.

With respect to your spouse, you are no longer being a victim of deception with each passing moment, but actively in control over whether it's appropriate to penalize her, or forgive her, or whichever choice steers the future in the direction you prefer.

She, on the other hand, is no longer calling all the shots - maybe she has been raising that child altogether the wrong way all that time, under the influence of guilt and the cognitive effort of deception. This is now something you can be aware of and correct for if necessary; as you can compensate for your jealousy-derived impulses, which anyway (speaking as a father of three) are only one of the many emotion-driven ways you regularly fail to be the parent you ideally would prefer to be.

More generally, "aesthetic preference" my left foot - the truth here makes the difference between steering or being steered. To be content with not knowing is also to be content with being manipulated, and that's something which I'd rank as strictly less acceptable than enduring the pain generated by my jealousy modules.