Exploring speed of ants
I don't think it's reasonable to try to do this in a species-independent manner, since there is so much difference between ant species. Leaf-cutter ants, for example, will build trails to forage 200 meters away from their nests. Likewise, ants vary by two orders of magnitude in size and the walking speed of an ant will vary accordingly as well. Finally, I don't think that you can reasonably exclude trail-building from your simulation, since that's a key ingredient of foraging.
Bottom line: pick a species to model and look for information on its specific mobility.