He wants to go, he's never been afraid of losing and he's not gonna start now, that's not who he is and if you really believe that about him, well I dunno. I just don't think that's his style at all.
That said, he wouldn't actually have to play a match til at least a week from today (well, a teeny bit less if you factor in a half-day for the time change
), if he decides wednesday not to go when he might be ok 5 days later.... that'd be really unfortunate but on the other hand if he leaves any later than Wednesday, he will not possibly be able to properly prepare to be able to do well there anyway.
why did he agree to the event? Because he likes charity events, and also he wants to have a good relationship with Elton, who has helped HIS charity a lot this year. That's the kind of person he is.