Stoick had ordered Spitelout and Sven to set up Loki's Maze of Terror. And obviously, the Twins had volunteered immediately.

Snotlout only helped because his father was doing it and something about "Jorgenson family pride".

Hiccup asked you to keep an eye on them because he didn't trust Snotlout and the Twins to be unsupervised.

Hiccup really would have gone himself, but he and Astrid were tasked to help Gobber make the Whirly-gigs and Fishlegs was tasked to help Phlegma with the pumpkins.

So, naturally, you were his only option left...

Well... It was actually either you or Gustav, but obviously Gustav would have been infinitely worse.