Why? There are plenty of warnings. The camp itself is a warning. If they have an NPC guide, sure, have them give a warning as well. But otherwise, if they go in and die, then they should die. ToA is very much about putting the fear into players and having characters die, permanently.
I swear these days DM's are far too accommodating, generous and forgiving. Sometimes I wish I could just yell, "SUCK IT UP, BUTTERCUP!" Back in the day, if a character died, it wasn't a cause for grief-stricken mourning, it was a reason for quickly scratching together a new one at the table and introducing him as Bob 2.0.