http://www.r4shops.com/r4i-sdhc-for-nintendo-dsi-1-4-3.html I have this for a DSi, and it works fine.
You won't HAVE to update, production of DS games stopped not longer after the 3DS was released, so DS games won't come with newer updates.
should be ok as the newest firmware is 1.4.4 which the card supports aswell,but i think that upsate is for dsi xl not 100% sure.