upgrading the DSi - on the cheap

So I got my 8 year old son what he says he wanted for Christmas. I was against it, but out-voted. But this thing is pretty cool. But without spending $30 a pop on every game, I need to educate myself on the alternative options. One of my friends told me about the R4DS card - and where to buy it.

>> video - R4 DS card
>> video - R4 DS
>> R4 DS Card - Firmware Download And Set Up For R4 DS
>> How To Put Nintendo DS Games On Your R4 DS

>> fighting anti-piracy

>> nintendo DS accessories

ROMS
>> http://romplanet.net
>> http://www.nintendo-ds-roms.com
>> http://www.romulation.net/

>> music has to be in AAC format (*.m4a *.mp4 or *.3gp)
>> and of course - the homepage

What I want to know is:
-the best ebook reader for it

-is it possible to watch videos/movies