I started playing piano so that I formed chords with 2-3-4 fingering. I got used to it so much that even today I involuntary go into this position even though I have spent hours and hours of painful (only in my head) re-training to use correct fingering 1-3-5.
One of the obstacles for me was learning scales with my weird fingering when all the sheet said 1, 2, 3, 1, 2, 3, 4, 5 and I had to convert that to 2, 3, 4, 1, 2, 3, 4, and some other weird stuff like that.
I have big hands as I am 6'6" (198cm) tall. I can hold a basketball in one hand with no problems and have a span of 10 notes on the piano. Playing chords with 1-3-5 feels really cramped, but then again it makes sense for so many of the things.
My opinion: Don't do the same mistake I did. teach you child the way it's proven to work. Don't re-invent the wheel.
