I wouldnt say tesco was crappy! It has pretty much all you would need, including clothing etc. There are lots of good bars and restaurants that are popular with residents and many others far and beyond south queensferry.
I have 2 children, one at tom thumb - a fantastic pre-school and nursery and the other at Echline. We chose to stay in the Echline catchment area just because of the area. Queensferry has a far larger catchment area and also bigger class sizes which wasnt something i was looking for. There is a nursery for children not of nursery age which is mainly directed to children who are of families in difficult situations, so i would aim for tom thumb or rosebury playgroup if it is for younger children.
There are lots of groups to meet up for, swimming lessons for the kids and other extra curricular activites including ballet by central scotland ballet school.
I myself would avoid the walker drive area, and maybe a couple of others by the top shops, but i doubt they are that bad. It all comed down to what you are looking for. Echline is nice, and the nursery and primary school are both within walking distance of all the catchment area houses.
Yes the buses could do with being better, but the queensferry council are looking into it just now. The bus to the gyle is reliable, as is the one to livingston, so i dont ever think you would be stuck if it came down to local transport!
Hope this helps and im happy to help with other questions! x