Oh my kids, 3 (almost) and 5, both have Kindle fire 8 tablets. They are getting proficient with a touchscreen.
I highly recommend some of the games like The Furchester Hotel in the CBeebies Playtime app. bbc.co.uk/cbeebies/watch/furcheste...
You won't have to worry about touch screen proficiency, designers work to make touch ui intuitive, at least to a degree. What you will have far more trouble with is teaching how these systems actually work. They will need to learn computer use, not just phone games.
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