Using the motivation !

Looking for some suggestions here...

At our apartment, we have this annual day coming up on the 1st of July. Usually, this is a social gathering - where there are sports and cultural event. This sort of "party" or get-together happens twice in a year - one during the new year's eve and another the annual day.

During the last new year eve, DS sang MS's "Kurai Ondrum illai" with great gusto ! He was so excited about it. Infact, when he paused a bit going from the first to second stanza, the crowd thought the song was over and gave him an ovation. He had the presence of mind to get off the stage (dynamic thinking ?!) and then come to us and tell us that he could only sing half the song...

Now, this year, he wants to do all - sing, participate in sporting event (cycling and swimming). He has even picked the song he wants to do - MS's "Oli padaitha Kanninai". This time DS's grandmom, who is a classical singer herself is at home and trying to train DS to sing.

Now the question we are grappling with is this - Although his intelligence level and skill levels aren't bad, the biggest inhibitor for DS, at most times, seem to be the absence of motivation; however, the participation in this party/event seems very exciting for him; he is willing to perform on stage and even put himself in a position where he knows he is not good enough and compete with other kids. Is there something that we can do with it? How do we take this and build it up from here, as a foundation for motivation for other things ? Any ideas?