Is there anything incumbent upon us after we removed our ihram and wore sewn clothes due to our inability to perform Umrah because of the severe crowding, knowing that it is a supererogatory act?

It is not permissible for someone who has entered into ihram for Hajj or 'Umrah to exit their state of ihram before completing the rituals, unless they are prevented (from doing so), based on the Almighty's saying: "And complete the Hajj and 'Umrah for Allah. But if you are prevented, then [offer] what can be obtained with ease of sacrificial animals." Ordinary circumstances, such as overcrowding, do not permit breaking ihram. Rather, one must remain in ihram until the circumstance passes. What you did by breaking ihram is not permissible, and you and your wife are still in the state of ihram. As for the children, the preponderant opinion is that it is not obligatory for them to continue their ihram because they are not held accountable. You and your wife must return to complete the 'Umrah if you have returned to your country.