The way I did it was coming back with a full party and enough perception checks to spot all six of the gas vents on the floor. Then move vases or chests on top of each one. That stops the entire floor from igniting when the traps are triggered.
Then I took the party out of the room to the north (I think?), came back with my MC and opened the sarcophagus for the loot. The gargoyles shot fire arrows but didn't hit that spot, and with no gas vents the floor doesn't catch on fire.
You might be able to disarm all the gargoyle traps, but I didn't try that and trap disarm kits are rare.
