WDS can be used to provide two modes of *wireless* AP-to-AP connectivity:
1. Wireless Bridging in which WDS APs communicate only with each other and don't allow wireless clients or Stations (STA) to access them.
2. Wireless Repeating in which APs communicate with each other and with wireless STAs.

As long as you are using a minimum of 5 channels separation you should be able to mount your Antennas on the mast you are presently using. I have no experience with the D-Link DWL-8200AP or the DWL-7200AP but are you looking to try and future proof your system? Both of these are dual band radio systems and unless any of your users have 802.11a wireless adapters then you would be wasting your money, the same applies for any "extra" speed they may quote you can get. 802.11a does not travel as far as 802.11g so you probably would need a "Repeater" for this mode. Since you have been looking at DLink eqpt did you look at the DWL-2700AP?