My kids 4, 6 and 9 all have iPod touch. I also have a nook and my mom has a kindle fire. The kids really have no interest in the nook or the kindle. I do have to say that both me and my husband have iPhones and iPads so we already have a ton of apps for the iPod. For us it makes sense to stay with apple and not have to buy new apps under
amazon or barnes and noble. My kids mostly use the iPod for games and music. My 9 year is also a runner so he also uses it to run with. He has used it to read a few books but it is harder to read on then my Nook or iPad. On the iPod/iPad you can download the kindle app and use it as a kindle.
I do have to say I have the nook color and I would go with the kindle fire. I say that because I found the kindle has more free apps and books then the Nook.
Hope this helps a little.