Ninasmum and bluebell have said everything I would.
I'm so sorry that you are having to make this decision so soon after losing your wife
I think that you have to think with your head, even though it will be very sad; what's best for tuppence is the most important.
My girls are left for 3-4 hours twice a day - they have each other for company and in morning and at lunchtime they get lots of play (and walks if I can). Then they get at least an hour in the evening for a walk and hazel gets extra play being a youngster.
I work 5 minutes from home. I'm able to work at home at least twice a week.
A 50 mile trip is a long way, then there is traffic, weather problems, what if you have to work late?
Even with a dog sitter/ walker or neighbours popping in I don't think that it's the right choice... As cruel and uncaring as that makes me sound towards your situation
Big hugs for you and tuppence x