I think I got much more understanding from the accompanying paragraph than the logline itself.

A logline needs to be as visual as possible so “venture into the unknown”… how does this look on-screen? Actually though, having read the additional paragraph, he’s not venturing anywhere unknown at all – he’s just going into the woods to find the giant’s house.

The dragon is somewhat superfluous to the story after the inciting incident. Consider this from both an audience perspective and a producer’s perspective:

Audience – They’re shown something as exciting and visually impressive as a dragon only for the dragon to not really feature at all in the rest of the movie. As an audience member, I’d be thinking “why isn’t the dragon the one getting revenge?”. Surely, that’s much stronger?

Producer – Not only do I have to have a budget for a CGI giant but also a CGI dragon that doesn’t feature after Act I. My guess is that every producer would say pick one because, not only does the story not need two, you wouldn’t get the budget for something that doesn’t really have much of an impact to the story.

I like the idea of the town having to decide whether to hand the boy over BUT people standing around deliberating… not very exciting! What else could they do? What is our hero of the story doing while they’re all deciding his fate? What are the villagers doing once the boy goes off?

How exactly is this boy going to stop a giant destroying the village? What is he going to discover at the giant’s house? I feel like the logline needs to hint at a bit more of a plan. We need to have some confidence this boy could succeed.

I would focus on either the dragon or the giant, scrap the other. Work out what the boy did to warrant this action from them, then give us a bit more of a clue what his goal is and how he’s going to achieve that.

Hope this helps.