Recently I got a cozy coupe for free from someone.  I came home and put it in the garage without saying anything to either child about it.  That weekend, they found it and immediately knew it was for them.  They did not ask.  In fact, he jumped in through the window (the door was on the far side) and was ready to go.  I had told her that she was too big for it, so he spent his first day driving around saying "I drive babies."  He dind't care what it was as long as it meant HE got to drive it around. 

If it failed to respond in a manner he wanted he would just grab onto the support bars and drive that way.

She was content to ride the tricycle.  Her legs are longer and much better suited to it.

Which was good as he was not sharing.  He would open up the door, slide over an inch, and when she didn't hop right in he'd take off with the door wide open laughing. 

Not our best day on sharing, but a good day of fun for both.