The quickest way is not the best, and the best way is not the quickest.
Quickest way is to just send them an NTSC disc. Many PAL players can also play NTSC DVDs which they send out as a variant of PAL. But not all PAL players can do this, and if they do, not all PAL televisions will play them.
The best way is to convert your video to PAL. You can do this in Premiere or After Effects. Then create a PAL project in Encore and rebuild.