Here an example with the cards.
Drawing from a normal card deck I have used for this, for my four players I draw king of spades (Bandit Captain), 8 of Spades (Ankheg Lurker) 7 Clubs (Displacer Beast twin) King of Hearts (4 Bandits)
To build the encounter I would put the Lurker Ankheg to the side as it will trespass on the battle later, and the Displacer Beast back in the deck as its twin was not drawn. Normally I would pick between the two other cards for the encounter, but they are both part of the Bandit Card group so instead I use them together for the encounter.