With Dean Moxey having been sent off in the same incident, Palace were forced to play the second period with 10 men and their numerical disadvantage proved costly when Mark Beevers struck late to secure Millwall a point.
Jedinak's powerful 30-yard drive flew past David Forde to give Palace a 34th-minute lead, before Delaney increased their cushion with a close-range header just minutes later.
After being booked for a rash challenge early on, Moxey was shown a straight red after being adjudged to have handled a goal-bound shot on the line.
Trotter stepped up to score the spot kick, and was one of several Lions players to have equalising chances in the second period.
The result leaves Palace in the playoff positions, two points adrift of Cardiff, while Millwall temporarily climb four places to 16th.