I have extended WiFi using antennas, particularly directionals. I have tested going diagonally across a parking lot, more than 300 feet. Where is your base station relative to the acreage? is the land flat?
Using uploaded packets, you may want to watch out for collisions. Maybe have the data packet contain current reading and 3 previous readings(time stamped). This is a simple way to allow recovery of drop outs. The data you are sending is probably small relative to the minimum packet size, so slightly larger packet will really not have a cost.
