I am very glad you have made a sensible decision!
Often parents think a little child needs a little 'toy' keyboard, but when our DS was born, mum and I were both learning to play a two manual Yamaha organ. To him, growing up, it was a great big 'toy', and by age five he was starting to read music, and also copy many tunes he heard.
So Yes, I think it is an excellent idea! (As it has MIDI it will also connect to a computer, for recording, multi tracking etc.)
I've just looked on the Yamaha site, and it looks like it may NOT have aux connections, to connect to an external amplifier, (which is rather strange). You will also need a power adaptor (if it doesn't come with one) and a stand, ideally robust and adjustable. (Maybe Dad can check out that aspect.)
Personally, I am not keen on the 'teaching' systems, but you don't have to use them, and I guess they will help motivate children.
[PS: I have done several other replies on keyboards and music, if you want to 'search' for them.]