If all that you want to do using Wix is to launch executables, Wix/windows installer provides multiple ways to do that.
I generally prefer using Quite Execution custom actions provided by the Wix toolset. Reason being, it allows me to launch executables without displaying any console windows, which otherwise would have required me to write custom action code.
Take a look at :
http://wixtoolset.org/documentation/manual/v3/customactions/qtexec.html
The examples in the above URL are sufficient enough to help you get started.
In order to use QtExec (Quite execution custom actions), you must include a reference to the WixUtilExtension when building your MSI. To do this, add the command line argument -ext WixUtilExtension.dll when calling Light.exe.