I've brought (well rescued from a skip) a 3rd hand bike for our 3 year old with the intention of stripping it down respraying the frame (John Dear green & yellow is this weeks choice) and tweaking everything. The only thing I'm having a problem with is the crankset which is a real bodge job consisting of badly machined friction fitted bushings and bits of plastic taking up some of the play all wedged into a bottom bracket shell thats about 25mm diameter.
Before I start wasting lots of time on this does anyone know if there is such a thing as a kids standard for what passes for bottom brackets or does each manufacturer bodge their own solution? Any ideas on where to get spares from? My LBS parts bin doesn't stretch this far and web searches have so far come up with nothing.

Not sure about the 25mm bit (sounds pretty tiny) but most kids bikes come with a one piece crankset and American/BMX sized b/b shell – if this is the case then you can pick up loose ball b/b sets on ebay pretty cheaply.

my youngest is sporting a skip bike that has a mostly plastic BB

it's nasty but not quite dead yet and I'm hoping she'll outgrow the bike before I need to alter it

(doesn't really affect her riding – suppose it slows her down but she doesn't know any different and it's not like we do massive long rides)