How do you create an optimized walk list given longitude and latitude coordinates?
As Steve Kallestad has said, this is a TSP problem, and there are wonderful free solvers to find approximate solutions.

It may be too much work for what you are looking for, but you may try use one of those solvers in combination with the Google Maps API, to find real walking distances beetwen your coordinates:
https://developers.google.com/maps/documentation/directions/#DirectionsRequests

(I have never used this API, so I don't know how easy or effective it would be)