Matthew 26:42 makes me think that He did NOT have a free will in choosing. "O my Father, if this cup may not pass away from me, except I drink it, thy will be done." That sounds very much as though what Jesus did depended on the Father's will and not His own.
But what was the cup He was speaking of? Most say the cross but look at the passages dealing with this.
1st clue what the cup was is seen in Matthew 26:38 Then saith he unto them, My soul is exceeding sorrowful, even unto death: tarry ye here, and watch with me.
Notice the tremdous stress His Body was under.
Mark 14:34 And saith unto them, My soul is exceeding sorrowful unto death: tarry ye here, and watch.
35 And he went forward a little, and fell on the ground, and prayed that, if it were possible, the hour might pass from him.
Again look at the stress his body was in so sorrowful even unto death.
Luke 22:43 And there appeared an angel unto him from heaven, strengthening him.
44 And being in an agony he prayed more earnestly: and his sweat was as it were great drops of blood falling down to the ground.
45 And when he rose up from prayer, and was come to his disciples, he found them sleeping for sorrow,
He was in agony even sweating drops of blood, so much was His body under stress the Father sent an Angel to give Him strength to make it through teh night and to the cross.
He was not asking that He not go to the cross in his request "let this cup pass from me" He was asking for strength to make it to the cross, but if God allowed Him to die in the Garden He said not my will but thine be done. God immediately answered the prayer by sending the Angel to STRENTHEN Him so He could make it to the cross.
I have seen this interpreted as you do by so many but the proof of the cup is in those passage that say he was sorrowful even to death and in agony sweating drop of blood. Couldn't be anything but asking not to die pre-maturely in the Garden because the emotional stress he was under. Great example of how God will come to us when we are under such great stress and yet many don't preach it that way.