If you have a good idea about what the clusters should look like, than yes, you can certainly build them using VNL.
However, it does not look like ATK-Classical has a pair-potential that supports InSnO compounds. You may then need DFT.
How big do you expect these clusters to be?
You write MD, but do you mean simple geometry relaxation, or actual finite-temperature MD at long time-scales? If the first, DFT should be an option.