It could be a challenge to convince one cat to put up with this. Some cats will trust their humans to carry them around indefinitely, but many don't like being held in arms for more than a few minutes, even it they'll happily sit in laps for hours -- it's all about trust and control. My previous cat would put up with almost anything; my current cats are doing me a great favor if they let me carry them upstairs at bedtime (when they'd follow me there anyway).
So you would probably have to approach this as an explicit training exercise, rewarding the cat for being willing to put up with something it initially won't like.Eventually it may decide that this is safe after all, and interesting, but I would not expect that to happen quickly unless you have an extremely cooperative cat.
Realistically, a better bet would be to get the cat used to a standard pet carrier.
(Other answers have covered the age at which it's reasonable to separate kittens from the queen. -- basically, you want to let her and the siblings finish teaching them basic feline social skills, and let them get some confidence in exploring the world, before you remove those supports.)