I had an arrangement today to take a DF out to a local nice town for brunch and bimbling around. It's been planned for weeks.
She doesn't drive and lives quite rurally, so I said I'm happy to drive, pick her up and drop her back.
When I arrived she came to the door with her DD who is 8, they both had coats on and shut the door behind them.
Her DH that morning had decided to go out for the morning on his very outting hobby so they'd between them that DD would join us in our plans.
They didn't think to give me the heads up.
Now besides the fact that I was looking forward to an adult catch up (my DC are pottering in the garden with my DH), there's no space for her DD in my car.
So we've had to change plans as we can't drive anywhere, I went in for a cup of tea and toast and small catch up with an audience, and now have left.
I'm going to enjoy some time to myself before heading back, but AIBU to think it's correct to give heads up a/ to manage my expectations, and b/ for logistical reasons.