I have no idea if Harry wanted to be part of the Tourney
I haven't read the book, only saw the movie.
From the moment Harry's name gets called out, he remains in a semi-stunned mood for the rest of the movie.
it's very possible i didn't pay enough attention but he just seems to kinda go with it. Accepts it but doesn't really seem to want to be there nor to back out.
He never says anything like "dude what the fuck, are all of you adults gonna endanger my life against my will?" or "hell yeah, i don't know how i got in but now i'm gonna win!". He's just...confused.