Danny,
You can get good information on windmills for water pumping here:
http://www.fao.org/docrep/010/ah810e/AH810E10.htm
This is the search result for "windmill" at the FAO documents site:
http://www.fao.org/documents/jsp/empty.jsp?cx=018170620143701104933%3Azn2zurhzcta&cof=FORID%3A11&q=windmill&search_radio=docRep&x=0&y=0
When you say you haven't received much rain, what has been your minimum precipitation per year? Less than 250 mm?
How deep are the wells? Are you on a shallow water table?
Drip irrigation can get very expensive. Other than irrigating a small kitchen garden, unless you anticipate earning a lot of money from your land, it probably is not worth it.
Have you researched hugelkultur for conserving water? If you don't have ready access to logs and other tree waste, you could use reeds. You would need to rebuild/replenish the beds more often, as the reeds would break down sooner.