The village isn't THAT small. I don't believe a full shot of the entire range of the village ground was ever shown, but the fact that the road was a half-day's journey from the village through the woods shows how large the grounds actually were. Woods included, it probably covers an area of at least several miles in each direction. I did wonder how large the original settling group was, but that's getting into too many picky details.

Spoiler thing... [I tried changing font colors to mask it... apparently doesn't work... grr]

The suits aren't all kept in the same place so no one necessarily connects the shed to the creatures, so whichever elder on duty could sneak off undetected to any hiding place... even if the whole shed bit seemed obvious.

Also remember that Noah was a bit crazy, so when he laughs at the beginning when the creatures howl, he very likely thought it was hilarious, after having figured out the whole scheme.