I already looked for the rulings and can't find them.

If I use Graceful Charity and send Peten the Dark Clown to the graveyard as the 2nd card I discard. Can I remove it and summon another one. Because it says that if it "goes to the graveyard" it doesen't say anything about being destroyed.

so I think im right

Well, first of, Graceful Charity sends both cards SIMULTANEAOUSLY, but aside from that, yes discarding the cards to the graveyard is the very last thing to occur, so if you discard Peten you CAN use his effect.

And yes Peten will get his effect destroyed or not, it just has to be the very last thing to happen, it going to the graveyard that is.

And the very last thing to happen means exactly that; the VERY last thing to happen...

So if you were to, let's say, discard Peten the Dark Clown to activate Divine Wrath, you would NOT get Peten the Dark Clown's effect because the very last thing to happen is a monster being negated and destroyed, not Peten hitting the Graveyard, which is what "missing the timing" is.

Same thing would be if you Tribute Peten the Dark Clown for the activation of Cannon Soldier. The very last thing to happen is damage being inflicted to the opponent's Life Points and not Peten hitting the Graveyard, so you wouldn't get its effect.