If they're good rationalists overall, they could also establish as common knowledge that they both timelessly decide not to predict/estimate their spouse would wish to know something which is known by themselves to be likely to bring about lower total utility to them both than if the spouse had never wished to know it, whether the spouse knows of this or not.

If they're good decision theorists, they will just not wish to know anything that their wishing to know would cause problems like that.

If they're good decision theorists they will just not make commitments that can only have downsides (relative to more careful commitments). It is of benefit to neither to arrange a system that requires mindreading how well the other person has mindread you and chosen to self modify to not want the thing that you would want them to not want to know. All that can do is allow extra opportunities for any deviation from good decision theory at any time to cause problems.