Our eldest daughter just turned 5. She's had a 12-inch BMX-style Giant for a couple of years now. It's been good, apart from being unbelievably heavy. It's getting a bit small, though, so it's time to upgrade. We got her a second-hand one, which I made a couple of upgrades to.
- a stand
- streamers on handlebars
- front and rear brakes, one lever-operated and compatible with little hands.
- decent tyres (ie not the ridiculous faux knobblies that seem to come standard round these parts)
- decent rims (not steel)
Light would have been nice, but 99.99% of kids' bikes are BMX-style (complete with stickers warning against riding them offroad or using them for stunts), so not much chance of that.
We picked up a second-hand one off eBay. Luckily enough, it had a front-mounted V-brake (although a cheap and nasty one), so we had a really good base. It even had aluminium rims, so using a hand-operated brake wouldn't be a complete waste of time.
I put a better V-brake on the front (some Tektro thing I had lying around for some reason), tidied up some cosmetic stuff and regreased the bearings. I've not had much truck with cheap cheap V-brakes (these were made of pressed steel(!)), but cheap cheap brakes in general are a no-go area for me anyway. I wanted something easy to adjust that wasn't too grabby. It worked well with the existing lever, which seems to have been aimed at little hands. The good thing about a fork with cantilever mounts is that you have a range of more or less powerful brakes to choose from, from cantilever up to extra-long V-brake.
We picked up some semi-slick tyres for reasonable money too (made by Cheng Shin, as I recall). The theory there is that they should last better than the knobbly kind and roll and grip a bit better. They were also slightly smaller, which means slightly lower stepover (good) and slightly lower gearing (also good).
Gearing is an interesting one. I took up track cycling about a year ago and this may have coloured my perspective a bit, because track cyclists talk an awful lot about gearing. Talking about what gear you're on is the rough equivalent of talking about the weather or something. I'm leaning to the view that it's important for kids too. In particular, I think lower gearing is a good thing for little kids (they'll struggle less on hills at the cost of going slightly slower on the flat). It's easy peasy to change the sprocket on a coaster brake hub too (although http://sheldonbrown.com/coaster-brakes.html has a couple of helpful hints I wasn't aware of), so I think I'll scare up a bigger rear sprocket and see how it goes.
It's been a good step up; our daughter's done pretty well picking up some new skills (like dealing with a higher saddle and using a hand-operated brake). In some ways I'd rather do away with the coaster brake (it makes starting off harder than it has to be) but it's what she's familiar with from her old bike, so it's a good transition. She's ridden it to school, both solo (and supervised) and attached to mum's bike (in which capacity it works better than her old 12"). Her little brother insisted on riding it back home. Who said pink's only for girls?