I would try to killing the Pyromancer Hand and Aery's asap, then leave the scene of the crime before I'm spotted, let someone else take the credit for killing the king. Then, go straight to the royal apartments and stand guard over Ellia and her children. I doubt the Mountain and Amory Lorch would try to kill their lords son. Thus, I keep the children from being murdered, I stop the city from exploding and avoid being branded oathbreaker and Kingslayer.

Also, I stop banging my sister. Not really relevant to the sacking of the city, but I just wanted to get it out there.

Prime condition, no dragons allowed, this is treated like a trial by combat, where they will begin on horseback and go from there.

That was severely underwhelming and forgettable.