In technical terms, there is no such thing as a PAL DS. Since it neither inputs nor outputs PAL video with any first-party hardware and add-ons.
And I haven't confirmed there was a PAL Game Boy Player. Don't see how that'd work, the GBA used more than 50 frames per second so older TVs in those regions would have a problem unless Nintendo used conversion of some kind.
iQue DS games require a Chinese system, but all others in theory should work anywhere (what about Korean games?). Do note however that Wii-DS connections, multiplayer, and DS-GBA cart features may not work between different versions. Like you won't be able to use a Japanese Diamond/Pearl on either the US or EU Battle Revolution. And US-JP eReader cards require a same-language reader unit.