The region lock is ONLY for DSi mode.
Currently there are NO flashcarts that run in DSi mode, so any DSi flashcart you have now will work on ANY DSi so long as you have it updated for the correct version.
yes the Acekard 2i should fine you might be buying a DSi XL with 1.4U this is not a good idea because of the region lock for the european games
for example if Pokemon Black and White were to be released in europe you ill not be able to play on the dsi xl