It is allowed for you to perform `Umrah on behalf of your father or any other Muslim. However, if one wants to perform `Umrah on behalf of their parents and themself in a single visit, then they have to perform `Umrah for themself first, and then they have to make Tahleel (removing the ihram attire) after every `Umrah they make it for themself or on behalf of others by shaving or clipping the hair and then going to Wadi At-Tan`eem to perform ihram from the beginning.