What character experienced change during The Last Lecture?

Jai experiences change in The Last Lecture.
The question is a difficult one to answer because there is little room for change in the narrative.  Everyone concerned knows that "the elephant in the room" is Randy's inevitable death.  This end point is the beginning, and as a result, no one really changes as a result of the lecture. For example, Randy started off as a "Tigger" and still is at lecture's end.  
However, one change we can see is in Jai.  At the start of the narrative, she is not comfortable with Randy delivering the lecture.  Jai was "leery of this whole last-lecture idea" because of how much time it will consume.  She was not comfortable with it because it was going to take something that neither she or her husband could afford to surrender:

We had just moved from Pittsburgh to Southeastern Virginia so that after my death, Jai and the kids could be near her family. Jai felt that I ought to be spending my precious time with our kids, or unpacking our new house, rather than devoting my hours to writing the lecture and then traveling back to Pittsburgh to deliver it.
'Call me selfish,' Jai told me. 'But I want all of you. Any time you’ll spend working on this lecture is lost time, because it’s time away from the kids and from me.'

Eventually, Jai gives into Randy's demand.  Her initial apprehension is changed when she attends the lecture. She sits in the front row and watches her husband, "the showman," put on his last show for the public.  Since Randy delivered the lecture on her birthday, he breaks from his remarks in order to present a cake and has the entire audience sing "Happy Birthday:" "As we all sang, I finally allowed myself to look at Jai. She sat in her front-row seat, wiping away tears with this surprised smile on her face, looking so lovely—bashful and beautiful, pleased and overwhelmed…."  The "surprised smile on her face" is a change from the frustration Jai displayed at the start of the narrative.