Someone is becoming a big girl

Everytime I think Miss C is at some certain stage in life, she goes off and grows up on me. DH is going on travel for the summer and will miss our 2nd birthday here. In order to give him an opportunity to play with Miss C and the gift he intended for her to receive then, DH went out and picked it out a couple of months early. His argument, Miss C is getting to be a big girl and big girls need their Daddies to help them learn certain things.
This is a picture of what DH got Miss C.

As you can see, adorable as it is, Miss C hasn't quite figured out how to pedal and is just a shade too short (hard to imagine!) so I ran over to Wally World this morning after a short stop at work and picked this up.

As you can see, it is just a little smaller, about perfect for now. It does grow into a bike with training wheels, a little smaller than the other one, just right for growing into. I think Miss C is really starting to get the pedaling thing down (I did load a couple of videos too, in case you want to check them out.).

We did already institute the "you shall wear your helmet if you want to ride your bike/tricycle" rule and Miss C doesn't seem to have any problem with that.

What is the right age to start riding a tricycle or bicycle? How do you teach your little ones to pedal?