My daughter is six and super-happy with the Nintendo DS. I have a 3DS that she also plays on sometimes. When she was 4, we bought one of those child-hardened Kindles and enrolled her in Amazon Freetime; she loved it.
Exactly the same progression with my five year-old. He still uses his hardened Kindle with Freetime, but for most gaming, really likes his DS I restored from a broken state on the cheap.
The games are for a young child. It is quite unlikely that Nintendo makes a game that is unsuitable for or disliked by people of that age. They are the one console maker who focuses on gameplay experience instead of graphics technology.
Get a PSVita instead it's a ridiculously underrated handheld and will be going cheap these days.
But as it was a young kid we're talking about I think it's safe to say there will be something on Nintendo that they're into.
My main point was more just you really do get what you pay for and if these things on iPads bother you then please vote with your wallets and buy products from companies that actually care about quality of their software.
Does not really answer my question. I don't feel that culturally these games bring much on the table. Why do you have to make 4-years old play games made for 4-years old? When I was 5 I wanted to play the games my 15 years old brother was playing.
The thing you want for this is called Privoxy. There are scripts out there to convert e.g. Easylist to Privoxy format. It should take less than an hour to get it all going.
Bonus, this can also be used to remove YouTube and other kinds of ads as well as all the phone-home "analytics" if that's your thing.
Some options:http://www.thekelleys.org.uk/dnsmasq/doc.html + ToDo's via Google
https://github.com/apankrat/dnswhisperer or more generally https://github.com/search?utf8=&q=ad+blocking+dns
There are also 3rd party services that provide this function. They have obvious privacy issues, but for a kid's iPad it might be an option.