This is going to sound silly, but to get a good feel for a lunar mission, including landing, you need to see Scott Manley’s Youtube tutorial, based on the Kerbal Space Program:

http://www.youtube.com/watch?v=7xXh5pwvY20You could choose to land vertically, as Surveyor did, but that approach is very inefficient, because you’re fighting the full force of gravity all the way down. A far better approach is to skim the surface as low as you dare, and thrust as much horizontally to scrub off the speed. As the velocity drops, so does the effect of centrifugal force, so you have to pitch nose up just enough to counter gravity.

Note that the optimal pitch profile is NOT a gravity turn.

I simulated such a landing in Simulink, a couple of years ago, My trick was to run the sim backwards in time, starting at rest on the surface. I was happy to see that GMAT supports this mode.

In Simulink, it was easy to use a Matlab function to compute the necessary pitch angle. The formula is easy enough, but as a GMAT newbie, I don’t have a CLUE how to implement it in GMAT.