Mention piano lessons to kids and watch them cringe. Mention playing really awesome games on the Nintendo DS and watch them get all excited. Now, mention piano lessons on the Nintendo DS and watch them squirm in confusion, a definite improved reaction that's all thanks to Easy Piano, which is now shipping to retail. It's a $40 game (of sorts) plus 13 key mini-piano that, if you're lucky, your children might confuse for the Guitar Hero: On Tour controller. Upon it gamers can learn to tickle the (plastic) ivories and even compose their own tunes of up to