We have the Amazon Fire Kids for our 2.5 year old as just had another baby and needed a distraction for him. It's amazing! The difference with the kids one is that you get the robust case, 2 year no quibble replacement however it gets broken but most importantly a year's subscription to the kids' package.
The games, videos and books are brilliant - easy for him to play and watch himself...without this package you would just have the internet and would have to find things for him to watch/play.
It is £5 a month after the year is up so we will see how much he still uses it by then. Also, we haven't used it outside of the house so don't know how well it works not connected to our wifi.
Best £100 we've ever spent! xx