Hi pokeplayer984!
I will not question that Littlefoot probably felt a certain satisfaction beside the relief about getting rid of sharptooth. We would not have wanted him standing there beside Ducky saying: "Poor, poor sharptooth!"
There was no need for a message like: How horrible we had to do it, but we had to for nobody would have demanded a great deal of sympathy from Littlefoot for that particular sharptooth. It would have either come across as Littlefoot being the utopian character bare of any negative emotion (which he mercifully isn't), or he would have come across as a hypocrite.
I don't doubt there must have been something like satisfaction for him to get rid of that sharptooth.
However, if it comes to the question on whether that was the reason for him to kill sharptooth and risk everybody else's life by doing so, I say definitely not!
Had there been a way for Littlefoot and the others to get to the Great Valley without taking another huge risk (which positively lessened their chances to ever see the Great Vally) I doubt not that they would have done so.
Littlefoot is just not the revengeful nature who would stand there proclaiming something like: "Never shall I set a foot (however little they may be

) in the Great Valley before I haveth not spilled my foe's blood and satisfied my thirst for revenge!" Nor do I believe that he would think along these lines (lest in a poor imitation of middle English

He must have seen that particular chance the terrain offered to attack the sharptooth (not one of those LBT 10 whimps that will almost drop death if a hazelnut sized peble is hurled at it) so what other debate would have been necessary. While he laid out his plan to the others there was a look of grim determination on his face; nothing like dreamy thoughts of revenge.
As for that look of Littlefoot's, you undoubtedly meant the one shown on this image:
http://mitglied.lycos.de/malte279/The%20la...0the%20bait.jpgI have a very different interpretation of that look.
To me it seems to be an attempt of an ingratiating look at Ducky who natuarally is not keen on being the bait. Look at Petrie, he is looking just the same way. There was a cut in the movie, so we don't know how long they needed to convince Ducky, but according to some book versions she accepted the unavoidable relatively quickly (being the only one who was able to swim (at least being any good at it) and lure the sharptooth to the deeper parts of the pond.
I don't think that Littlefoot or anyone imposed that task on her because they just didn't want to go. Neither Spike's nor Littlefoot's strength could have been spared at the rock (theirs wasn't even enough) while Petrie was least of a swimmer and also presumably very slow on his tiny feet (he rode most of the time; so did Ducky, but there are more scenese in which Ducky is walking than there are of Petrie doing so).
Back to that look; it really doesn't seem like the evil smirk we see from someone endulging in revengeful thoughts (there are good examples from Ozzy and Cera).
While I do not question the possibility of satisfaction on Littlefoot's part after Sharptooth's death I really don't think it was among the main reasons for him to kill sharptooth.