Need help re travel costs adult disabled

My sister son has moderately severe mental disabilities. He was in further education and getting a taxi paid for him to go to school. He is now 19 and he’s going to an adult daycare instead from July. He will obviously have to then claim his own universal credit and PIP to my sister will lose all her money for him for universal credit and Pip obviously she loses she still will have to manage it because he’s not got capacity. The issue is today. She had a meeting with the social worker and she was told that he has to pay fully for his taxis to the daycare centre out of his pip they have a mobility car but obviously he can’t drive it. My sister can’t drive it. Only the Dad drives it but he works so he can’t be driving him to the daycare. is it true that it has to be fully paid by The disabled adult considering the taxis I’ve been told a £60-£80 a day and obviously it’s PIP would only be about 600 and his universal credit about 400 because he’s got a motor ability car. Does that mean you can’t get any help with a taxi or someone to drive the car? Can anyone help please?As no way he can pay 20 days x 60/80 costs as won’t have enough income to do this.