@pleonasm - I absolutely adored my bicycle when I was a kid and it was a secondhand one my father bought from an ad in the newspaper.
Something I think people should remember is to teach their kids how to look after the bikes themselves. Filling the tires, oiling the chain and so forth. Maybe even fixing a puncture for the older kids.
Bike maintenance isn't difficult but it's a really good habit to get into, especially if you have a secondhand bike rather than a new one.
If you do all this stuff for your kids instead of letting them learn how to do it themselves, they could end up spending lots of money taking their bikes to the shop for fixing rather than spending a few minutes on preventative care.
Plus kids are happy to do that kind of work. When you are proud of your bicycle everything about it seems like an adventure, even filling the tires.