There are lots of other solutions. Having seen some of the things I"ve seen, if I had it do all over again, I'd never go with training wheels.

there's this for little kids:

http://www.likeabikeusa.com/ which bypasses training wheels entirely and teaches balance skills,

and then I have read of many sucesses where the seat was put all the way down so that a kid can just put a foot down whenever they need to, and no training wheels were ever used. I know this doesn't solve your problems, but I'm just amazed when I see two and three year olds on two wheels.

Irulan