Oooh but wait! I totally dismissed this too quickly.
What if we took a page from Quirrelmort and
actually fixed the whole fiasco (still in henge, using mostly seals since we're low on chakra). That way, everyone still gets dq'd when their henges pop, no one gets murdered (or less do, at least),
and we have the completely believable excuse of not wanting anyone to get seriously injured in the chaos to clear us of suspicion.
(Which is of course why we snuck away from STL to investigate the commotion in the first place -- and STL is all huddled up somewhere else because they were smart enough not to join the ever growing throng when weird shit started happening. -- And how did we all know what was happening out front? Hinata.)
We can even "try" to remain anonymous (hidden out of view and in henge) and "try" to bail and hide when we get everyone to chill and stop the stampede (hopefully being caught by a proctor).
Steps:
1) Break several filled life-preserving seals to both disperse the sake cloud and
temporarily knock most everyone out from the suddenly increased levels of CO2 (don't worry, we're in an open area so it should disperse fast enough that no one dies)
...
...
2) Try to escape, and inevitably be chased down by a proctor
3) Surrender, explain ourselves, and take the blame for the explosion seal going off as us trying to disperse the cloud (thinking it was poison and everyone was rushing headlong to their deaths). It didn't work so we tried something more drastic, which did.
4) Claim we saw someone use a jutsu to create the cloud, and then ran off faster than we could track them
...
...
A few issues, but maybe not entirely unworkable?