Very nice Goaly!
  they make motors just for that type of fan,not a prop but it powers multi fans from a single location.  They are generally belt driven and used for commercial or industrial applications.
   The wheel chair motor should work but isnt it a DC motor?  you'll need a converter or power it with a battery.
   I would think any 1/2hp AC motor would do the job and you can use pulleys to get the proper rpm.
  Cant wait to see it finished!   
