Pacify: Each round, the first time this creature makes a melee or ranged attack, its controller must pay 2 mana during the Declare Attack Step, or else the attack is canceled. Pacify does not affect counterstrikes.
Sweeping: This attack has a wide sweeping arc and can target and strike 2 different targets in the same zone. The second attack occurs at the end of the attack sequence from the first attack. Start a new attack sequence beginning with the Declare Attack Step. Note: The second attack cannot be made against the same target as the first attack. If there is not a different valid target for the second attack, then the Sweeping trait has no effect this round.
So sounds obvious that extra strikes you get from doublestrike and triplestrike would be cancelled, but not the extra attack you get from sweeping.
The scenario I am imagining is two opponent creatures, one guarding. I have one creature with the pacify enchantment attached and a sweeping attack. I make the sweeping attack on the guard, but choose not to pay the 2 mana indicated on pacify. The first attack is cancelled and the guard marker is removed, freeing up my second attack for the other creature. Is it correct that I can do this? If not, why not?