I also think, if it is mandatory for you that a parent stay, you need to be explicit and state it. Ie what would happen if a parent said to you, 'see you at pick up time'. Its a bit late to say then, no, you need to stay. Are you thinking of something at a venue? Would you feel different if you had something at home? I do think alot of people would expect frop off and pick up at the end.