Last year a colleague covered some hours at work for me (just a couple) so I could see my son's assembly at school. She has now asked me to return the favour but I have said no because it would mean I couldn't pick ds up from school and would have to ask dh to take time off to collect ds. Ds had sn which is why I can't just ask a friend to collect him. My colleague seems a bit put out and I have apologised, but I was hoping she'd be more understanding? I would happily help if I could do it without it affecting ds.