Hi -
It seems to me there is a great deal of 'snobbishness' around children learning to play any instrument. Do parents REALLY want their child to learn for his/her own sake, or do parents want bask in reflected glory when they perform at their first concert - whether it be at school, or the Albert Hall.
As a TA I taught 'informal' music for around twenty years - introducing children who had keyboards to very basic improvising and making up their own tunes; ten years in primary school with recorder clubs, ran a percussion club for a while, and coached children on percussion to accompany the Christmas 'production' for ten years.
But all of this was for FUN - no ambition or desire to take Grades; that can come later, if a child enjoys making music and is prepared to put in the work.
A digital piano, ideally with weighted keys and 88 of them, (though you can manage with fewer) is quite adequate to start a 6 yr old. Personally, I favour a Keyboard, which can be more fun in the beginning than a piano. Either can be connected to computers for recording or multi tracking. I would steer clear of 'flashing light' tuition systems.
[I have replied many times on this topic, so if you search my name with piano, keyboard etc you can probably read several articles on this.]
PM me if you want more help.