head off for more sightseeing

[keannu]

What does "head off" here mean? The dictionary gives me only the meaning of "disturb", which doesn't seem to fit it.

mo3-46ex) We finished eating and decided to head off for more sightseeing. But when Rob and I went to the garbage can to throw away my lunch bag, I heard a strong voice ask, “There isn’t any food in that bag, is there?” It was (c)the man who had been watching us. I didn’t know what to say. “No, I ate it already.” “Oh,” was his only answer, with no shame in his voice at all. He was obviously hungry, couldn’t bear to see anything thrown away, and was used to asking this question. I felt bad for the man, but I didn’t know what I could do.

[emsr2d2]

I'm not aware of "to head off" meaning "to disturb"! It can mean to cause something to change direction or course, to put it off its original planned direction.

However, here it simply means "to commence a journey" or "to leave your current location".

It's time for me to head off now. I have a job interview to get to.
My parents came to visit yesterday. I thought they would never leave but they finally headed off around 9pm.

[SoothingDave]

If my head was off, I would find it disturbing!