You have enough coinage in your hand (4) to beat the next best of 3. But you need two actions to play them, which would then pass your turn with no guaranteed win. Fortunately, you have Last Laugh in your keep. Here is the solution:

1. Play either one of your cards into your keep.
2. Draw from your (empty) pile, ending the round.
3. With the final action from Last Laugh, play your other card into your keep.

This way you have your 4 coins, and the round is over!