Cycling for dummies (and procrastinators)

“I’m going to do a 100km cycle ride” I enthusiastically declare to my family a couple of weeks ago. Ok, so I haven’t ridden a bike since I was 10 and I am pretty unfit and yes I’ve been procrastinating about starting cycling for months (three different bikes sitting in the shed gathering dust) but come on family do you really need to smirk quite so much?