I think you are on the right track by separating your weather sensors using different motes. I have a weather station and I used to have everything combined into one, wind speed, direction, rain sensor, temp, humidity, etc. The code got pretty complicated, plus the temperature was never correct because it was partially exposed to the sun. You want to locate your temperature sensor where it is shaded and out of the way. You want your wind sensor located out in the open so you can sense the air movement. The Davis anemometer will work on 3.3V. The code out on cactus.IO will need to be modified to be low power if you use batteries. As far as the Pi Gateway goes, you will just need to add some new user metrics for the wind speed and direction. If you would like I can post mine and you can modify things to your liking.