I have to go to a sweet16 this weekend, so i asked my step-bro to drive me and now theres a change of plans?

so i have to go to a sweet16 blah blah blah, and i asked my step-bro to drive me on friday and then he'd have to go to work. but now my friends mom called and said that they wont be home on friday, and theyll still be in manhattan at 11pm, and its not like ill ask him to drive me at that time cause he has work so i asked my dad and he said okay, but what do i tell my step-bro now, i kind of feel bad about messing around with his plans?