I'm interested in purchasing a tablet for my son as his big Christmas present. (He's always making a mess out of my iPhone...so I want him to have something to call his own). There are sooo many on the market to chose from! I can't afford an iPad...so that's out of the question. I've narrowed it down to the following: LeapPad 2, Innotab 2, Nabi 2, and the Kindle Fire (not the HD one). Any suggestions or recommendations? My son is 3.5 years old.