It is not crazy at all, and this is coming from a rabid ipad hater.
I have two sister-in-laws aged 25 who don't own a PC/laptop, one has an android tablet+phone, the other just a phone - both of them are completely happy with those devices being the only way they can access the internet, they don't even want another device
Different generations use the internet in different ways..
That is a choice they make now, there are a huge number of careers, the majority(for now) in which considerable IT usage isn't required. But then 99% of people don't use most of the maths they learn in school, nor english lit, nor french/spanish/german.
School is about learning to give children OPTIONS for the future, ipads severely limit their options. If you get into a future career in programming, familiarity, being comfortable with a proper computer, being a competent typist, etc, is all going to make a difference.
What other things does your sister not use that she learnt at school. Most people use a small subset of what they learn in school, the entire school system is built to start off as a very broad education narrowing at each level till you pick one or two area's to do a degree in and a general career direction.
THe argument isn't that everyone needs to know how to use a proper computer, the fact is that with a hugely IT heavy job market, which increases by the year with more and more small scale stores running via computers rather than pen and paper, means basic computer usage is the very minimum kids should be taught and have experience with. Being taught some computer fundamentals and some programming languages will be much more beneficial to a far greater number of students than French/Spanish is right now.
I know of essentially no one, beyond going on holiday, that use the second language their learnt for work, where as(because I know a lot of programmers more than anything) huge portions of people I know would have benefited from learning programming earlier.
Getting rid of real computers is completely retarded and any head teacher looking to do so is short sighted, stupid and well, just one of the all to common people who jump on every trend.