I'm afraid that you can't map clusters to C structures like that because LabVIEW clusters are based off of internal multi-platform based constructs. There are some examples of passing clusters and using the "Adapt to Type" setting in the Call Library node, but that requires creating CIN-like code where you need to adapt LV data types into something else. I don't recommend going down that road.
Instead, I would recommend doing the wrapper DLL approach. If you have access to CVI, I recommend that because of the ease of importing CVI build DLLs into LV. If not, you can use Visual Studio or some other C compiler. Either way, create wrapper functions that take some basic types (strings, integers, doubles) from LV and then calls the Win32 API. Then convert the result back to basic types. This allows you to use the Call Library node.
Hope that helps