Is it more befitting for me to give money to my parents for them to perform Umrah with it, or for me to perform Hajj with it for myself?

If you have not performed the obligatory Hajj (Hajjat al-Islam), then it is incumbent upon you to hasten to perform Hajj immediately with the money you possess. It is not permissible to give precedence to your parents with it, because the right of Allah Almighty is attached to it. However, if you have already performed the obligatory Hajj, then there is no harm in giving precedence to your parents with the money you had set aside for a supererogatory Hajj, so that they may perform Umrah with it, especially if there is a legitimate benefit in doing so, such as giving precedence to people of virtue and parents.