I had a Wii and it seems a similar story with U that while there's not a huge selection of games, there are some absolute belters. Why are handhelds a no-go out of interest? The 3DS started slow but just gets better.
I worry about his eyes!! seriously my older boy ( boy lol hes 18 in a couple of months bless him ) had a handheld from a young age and his eyes seem to have suffered as a result.
Now i am no Optician and it probably is unrelated but i would prefer a larger screen, however i do appreciate that the wii U control pad also doubles as a handheld so it might be a blessing or a curse.
Also I have seen some of the games he likes and have been pretty impressed with them, plus Mario cart 8 is out soon and I love that, so with my eyes in mind a bigger screen is a good thing.
Same with films I think, not meant to watch a 3d film or heavily play the games until their eyes are developed?
I have a Wii U. Unfortunately it's not used as much as the PS4 or Xbox One - primarily because my kids are older.
However the Wii U is an excellent console and Lego City is a brilliant game. I would highly recommend especially for young kids.