I am afraid I would have to agree with the view that your life style is not conducive to dog ownership.
They are social creatures who crave human attention and, in my view, simply cannot be left for the whole day, even with a dog walker coming in.
I don't say this lightly as I waited over 25 years to get my dog, I have been a dog lover all my life and was desperate to have my on, but I had to wait until I was no longer commuting and working. I settled for a Maine Coon in the meantime, who are very dog like and can be trained to do tricks etc!!
Dogs not only require company, they are also a huge commitment and even though I am at home all day, I have to plan all my activities and to some extent my daughters around the dog. You can't have a spontaneous day out, even going out for the evening - meals, theatre etc can be difficult as I am always clock watching to be back from my (admittedly) young dog.
You need to look at the costings ( as stated above) they are expensive, to feed, to insure, general vets bills, inoculations, neutering, worming. You have to commit to training classes, although they can be great fun for children as well. You have to commit to getting up much earlier every day to walk the dog before work - in every weather imaginable (and unimaginable!!). Forget lie ins - your furry child will expect to see your smiling face nice and early every morning!
But, having said all that, I adore my pup and have never been happier, we both love the walking and have made so many new friends, we love the training and he makes me a very proud mum! I love his company, his big brown eyes, hearing his steady breathing as we both lie on the sofa - the list goes on - I could not imagine being without him, BUT I waited until I could commit all the necessary time and do with for pleasure not as a chore.
You really do sound like your are thinking this through properly, and its not an easy decision but please make it in the interests of the dog and not just your family