I don't think that it is a good idea to buy a bike for your child to grow in to, unless you're not planning to use it until he/she does. This is mainly because of the safety concerns more than anything else, as a bike that is too big for a person is hard to ride, especially if it is your child's first bike.
I think that if you want to save money, it is better to buy a cheaper bike from Kmart (or some place like Kmart) and have it fit them, and then you can buy a more expensive bike as they get older.
