Hi there
Certainly the only way to put non-standard styles into the KN2600 is through SD Cards because there is no other loading method such as floppy disks. Transferring styles via USB cable from PC to KN2600 is also possible but by the way you describe their technical competence I don't think that route is possible.
Now it's one thing to have the right styles for western music it's another thing to have the sheet music unless of course they are very talented and play by ear.
I take it that there is an increasing demand for western pop music at weddings in Indonesia? Please e-mail me on RMepstead@btinternet.com if I can help further.