Hallo, Sunilor. There is no way to apologize... we will make you check your spelling. 
But let's see:
I like that the stated goal of killing the dragon is only at the end of the story, after going through other missions - dragons HAVE to be extremely dangerous, so much that you need all help and all the luck to seriously wound one.
For the final reward in the Viking-like fantasy, you definitively have to start with a huge feast thrown in the players' honor. That is a must. The rest of the reward should be something to drive other adventures - perhaps a ship under their control? Or they become 'defenders of the crown' (think of a fitting title), which would make them minor nobles... and bound to help to their king in any way. (Oops, there are three angry giants terrorizing the country. Oh, somebody has to go on a diplomatic mission far away to prevent a war - that kind of stuff.)
Yes a feast is good! Im thinking that maybe they will be rewarded with a castle. But since they are famous heroes by then everyone wants their help
all of the time. So it will get so irritating that they might just move away so they will be left alone. Or help everyone:)
Another idea I have is that the rpc find a egg in the cave after killing the dragon. And ofcourse alot of people want the egg becuase the one
with a tame dragon by his side would crush all who opposed him. It will be up to the rpc to either give away the egg, sell it or maybe
try to destroy it or hide it. Maybe none of the leaders are good so the rpc dont want them to have that kind of power. So, when they
are supposed to be heroes maybe they will be threated as criminals when the leaders hear they are running away with a dragon egg.
Or something like that...
Don't put the four wizards into the town's inn, that smells of a bad computer game. Make them important characters, with their own homes, libraries, etc. Their arguing should throw any city council off track. Make them hard to approach, and let the players use their smarts.
Yeah you might be right, that would also make the campaign longer and the visit in the town a little bit more interesting.
But I dident actually mean "wizards". I thought of them like some old confused men, that no one cares about, who was
just talking in the inn. And maybe they see themself as wise wizards or something but they arent, just some old
fools always arguing in the inn about all kind of stuff. And ofcourse they all are wrong but somehow in the end
it anyway leads the rpc to the dragonknight:)
But I like your idea aswell so Ill have to think about it! Maybe the wizards arent wizards but somekind of
council that gives the king advice. And they have divided oppinions on how to kill the dragon so the king
is just as confused.
The four ways to kill the dragon can be all wrong, but each should offer at least some bonus for the final mission, related to the rumors. The halflings could offer healing herbs, so that they don't expire from the poisonous breath afterwards. The elves might know a few words of the draconic language - which might be enough to make the dragon pause at a critical moment. The temple could belong to a completely different deity than expected; but it still might offer blessings for warriors on a noble quest. And there is no spear; but there might be a useful sword underground. Simply, twist what is already expected, and make the journey worth it anyway.
Great advice! I have already thought of healing herbs but the idea that the elves know a few words of the language is just brilliant!
And the temple idea is just as good! I really like it, I just have to figure out what kind of deity they worship. Maybe they are evil?
The useful sword thingy is also very good! Or maybe there is a last survivor of the dwarfs down there that tells them that the
spear is just a legend. But maybe instead of giving the rpc a sword he enchants their weapons with magic runes!!
Why dident i think of all this earlier???

As for the halflings... well, they could have some weak poisons, that only knock people out - and pretend, that those, who misbehave will feel the real thing. And of course they could have problems with someone who sees through the charade.
I actually came up with a idea about the halflings im quite satisfied with. Hmm its hard to explain. But they are so kind and loving in their peaceful land that its actually a kind of defence.
Its a curse. The place its so wonderful that the RPC will have hard to leave, many have come and stayed there. But the victim dosent know how long he is staying and sooner or later he
dies of hunger and thirst without even realising he have stayed so long. So the RPC can find skeletons from earlier victims in the land and then, maybe before its too late,
starts to realise the danger they are in.
But I have hard to get a reward into this so maybe ill change this idea even thou I really like it. Maybe the RPC never reach the halflings homeland, they get killed in the woods.
But the Halflings revive them with their herbs. When the RPC asks the halflings explains they have no poision but are willing to give away some of the herbs to help the char
in their quest.
Thanx for the GREAT ideas!!! Really helps alot!!
But im still open for more ideas and thoughts!:D