but a simple laser bounced off low cloud could be the right answer.
Going through walls, thick vegetation, etc will shorten range.
Only slightly more expensive would be to set up a couple routers, reflashed with dd-wrt, with Yagi antennas to maximize range and avoid interference.
Isn't the frequency wifi uses not particularly good for distance?
This wouldn't necessarily work well in the cities or suburbs, but is probably fine for Keven.