Players want to burn down the Hall of Illusions

Our first two sessions were great, players started out just enjoying the carnival for what it is, then the intrigue picked up with finding and interrogating Kettlesteam, getting the mood up to maximum, and getting the chance to speak with Witch and Light. The players are aware that there is much more than Witch and Light are letting on, and after encountering Sowpig in the Hall they have correctly assumed that’s where some shit goes down.

I feel like I’ve done a good job giving them multiple hooks to eventually get the answers they need. The two Witchlight Hands of the party are gonna recruit some of the other staff members to either unionize or join Burly’s heist to get the watch, and two other members are on the path of “have the most fun, get crowned Monarch, and ask a boon of Witch and Light”.

The part I’m worried about is that the last two more…chaotic…members are dead set on arson. They figure that the Hall is the most important location, they reckon that’s where the portal is. They returned Candlefoot’s voice and were able to convince him to close the Hall down for an hour so he can have a second try with his Palasha proposal, so no one else will be around. They feel setting the tent on fire is certainly a good way to get the attention of W&L, who kind of brushed them off without giving substantial answers. But if they’re able to go through with it I can’t see how they’d be amenable to work with anyone associated with the party. I feel like that’s a great way to tank any chance of assistance with getting into Prismeer.

I certainly don’t want to railroad them into other options if I can help it, but I feel like there’s no organic way other than having W&L find out and put the kibbosh on things (by force or otherwise) or else they face way too severe consequences - but that seems too deus-ex-machina in my opinion.

Any ideas on less heavy handed ways perhaps lead them down a different path? Or, conversely, thoughts on how to handle the aftermath should they actually go through with the plan?