We will do lots of practice walks over the summer if we do choose this setting though
Walking in the summer when it's light and warm out is VERY different to walking in the dark, cold, wind and rain in the winter. Trudging up a hill carrying your child's bag, trying to manage an umbrella, and walking against wind and horizontal rain is utterly miserable as a one off, let alone doing it on a regular basis.
It's also not the same as doing it after your child has been at nursery all day. Plus, you're going to have to do it twice. Walk there, drop off DD, walk back (wet and cold in winter), get home, and then do the same thing all over again. Possibly in clothes that are still damp from the first walk. Then you'll need to dress DD (again, possibly in wet and damp clothes) and walk her home again after she's been busy at nursery for eight hours. She'll want her dinner and a bath, not to be walking home in the cold and rain.
I think you have a very idyllic idea of what it's going to be like. It's a bit like dog-walking - in summer I love it, going out with the dog in the sunshine, gorgeous views and fun walks across fields or at the beach. In winter, it can be utterly miserable. It's cold and wet, they get filthy and no matter what you wear, you come home either soaked or freezing cold, or both. Then you have to go back out again later in the day!