I know the OP was posted a while ago (time flies!), but just in case anyone might want to read another opinion, I'll say balance bikes (or running bikes, even push bikes) do work very well for some kids. They aren't that expensive, and eliminate the need to even buy a trike/tricycle, because a kid could skip that step, and jump to a balance bike really early.
Some balance bikes can be transformed from trikes to bb, etc. Even when kids start pedalling, they might use both pedal and balance bikes at the same stage, but for different purposes (i.e. for bumpier trails, they may feel safer with a bb, as opposed to riding a pb).
Yes, removing the pedal crank of a bike is a great option to save some money, but always not forgetting safety, as kids must be able to plant their feet on the ground while seating. Smaller kids may find it difficult even on the smallest of the pedal bikes.
Another option would be to buy a 2nd hand balance bike.
Every kid is and learns differently. If in doubt, head over to your local bike store and let them try a couple of balance bikes!