WIBU to not go straight home

[FabiantheFish]

I have been told I can leave work an hour early today.
My DH is a stay at home dad and is at home with our 3 DCs.

Would it be really unreasonable no to mention that i am leaving early and to go to the library of a cafe and spend an hour reading quietly by myself then go home at my usual time?

As a sahp myself I think it's not the end of the world but a bit mean. I'd probably do something like the Sainsbury's shop instead to make good use of the time.