Just picked up this thread. Laudable aim to develop child friendly blood glucose meter.
You need to break down the steps involved eg:
knowing when to test
washing hands (if required)
protection for another person involved in testing someone else's blood (may not be required, depending on presence / absence of skin wounds)
fitting test strip to meter (some come in tubs, so user doesn't have to load each strip individually)
swtiching on meter (sometimes inserting strip does this automatically, which is a good feature)
fitting lancet to finger pricking device (many people don't change lancet each time, although that is recommended)
pricking finger (relatively painful, more so than insulin injection)
obtaining sufficient blood for test (less the better)
touching blood drop to strip
waiting for result
acting on result
As you'll notice, some of those steps could be done by a very young child, while for others, particularly knowing when to test and acting on result, require much more maturity.