Thank you all again for your guidance. :-)
OMG, this is so much harder than I thought. I guess you can tell that I get pretty anxious when making a big decision. London is huge and there are many different areas. ...I don't know how the atmosphere, vibe, and community are in each area so do forgive me for asking such basic and silly questions. 

So my husband will be working in Mayfair, guessing he'll take the tube to Bond St Station. Do you think it'll only be a 20 minute commute on the train from Clapham Junction?
If we do send our children to The Dolphin School, we will for sure live in between the Commons because I really want to have no more than a 15 minute walk to school.
So the reason why Dolphin has openings is because it's strongly Christian? We are Christians(Protestant) so that's actually a plus for us. We did find the school to be extremely warm and nurturing. All the teachers we met were very sweet and caring. Besides the facilities, are there any other cons of the school? I.e. The academics?
I will probably out myself... but we also really liked Sarum Hall in Belsize Park. Great facilities and still seemed like a nurturing school. Big with the Arts which is a huge plus for us. But again, how is the community in that area? IS it similar to Northcote Rd? BUT sadly they don't have spots.
However, we are on the top of the waiting list. (fingers crossed)
St Mary's in Hampstead does have spots. We liked the school but unsure of the Catholic Ethos. It seems very Catholic.
I think the Kensington area is gorgeous but seems a bit sterile. And I will be taking the children to Hyde Park for green space if we live there... yikes.
I guess in my dream world we would have a quick walk to everything, i.e. school, a large park, church and work for my husband. If we live in the Belsize Park area, he could walk through Regent's Park or hop in a cab or hop on the tube.
If we live neat Northcote Rd, my main social life, running errands, and walking, will be on Northcote Rd. You need to take a bus to go anywhere else, correct? I.e. Battersea Park, swim lessons for the kids, stuff like that. So in my mind, I'll mainly be in that little area. I don't know.
Ack, so many questions! I'm totally ruminating. Really grateful for all of your help.