Seen some cheap Samsung tablets that you can get apps for kids also iPad Mini is cheaper now and if you jailbreak it you can get a lot of free apps for kids
if you talking about kids below 5 years old, any cheap but decent tablet that has Android 4.0 and above should be good. young kids have a tendancy to crack the touchscreens.
ipad mini for kids... buy a good kid friendly case for it, and you are set.. dont waste $$ on cheaper tablets, just go straight for it...
any tablet....a kid wont care, as long as its got proper casing so it doesnt get damage, which is highly likely!
you know, they also sell those special tablets with software on it specially made for kids... simplified you know