DH, myself and DS are all visiting his grandad.
Fair enough, we don't really have time on the way there.
But he's saying "No, we aren't going McDonald's".
My reason for wanting to go isn't just because I fancy it, I suffer from bad migraines and get terrible sickness afterwards.
Salty chips, or particularly McDonald's or Burger King, usually helps massively when the sickness is there 
I've said but it helps me feel better. He says no we aren't going, just have something else in the house if you're hungry.
I feel a bit 
WIBU to tell him to continue on with the taxi on our way back but stop off at McDonald's for myself and meet him back home?