I've had a lot of success with a Raspberry Pi 3 and a 15" monitor. My 3 1/2 year old learned how to use a mouse nearly instantly and can click around on the desktop.
The Pi is $35 and has HDMI out and lots of USB ports. It's pretty great.
The Pi is $35 and has HDMI out and lots of USB ports. It's pretty great.
What software do you have running on the Pi for your 3.5-year-old?
A colleague of mine had a lot of success with Edubuntu. [2] Her six-year-old is a whiz at the command line. Again with the keyboard use, so not quite appropriate.
I'm still looking, basically. He likes clicking around and seeing that he's having an effect on things, but he usually ends up at YouTube, which isn't so great.
[1]: kano.me