There's a few elements that stand against the idea of Jar-Jar having been mind-tricked.
Yoda and Windu were in the room when the decision was made. While Palpatine can evidently cloak his own capacity, mind-tricking someone right in front of a Jedi Master would have been an incredibly risky move.
“The Senate must vote the Chancellor emergency powers,” Mas Amedda suggested at last. “Then he could approve the use of the clones.”
War, you mean, Yoda thought sadly. What other use was there for an army? Not in centuries had Yoda so wanted to comment, to interfere in the politics playing out before him, but he had already said what was needed, and the Senators had not grasped his meaning. He held his peace. Jedi serve. Make laws, we do not.
The Senators looked at one another. Plainly, they thought the idea was a good one, but none of them wanted to be the one to propose such a huge change in the way the government ran. Finally, Jar Jar Binks stepped forward.
“Mesa proud to proposing the motion to give yousa honor emergency powers,” he said to Palpatine, and the matter was quickly settled. Jar Jar would bring the motion up, and the other Senators would support it. When it passed, Chancellor Palpatine would approve the emergency use of the clone army.
Attack of the Clones: Junior Novelisation
In the adult novelisation, it's made clear that Palpatine has maneuvered the Senators and the Jedi into a blind alleyway. Binks is merely the conduit of a decision that they've all come to and after some very slight prodding from Mas Amedda, he finally works out what he's supposed to do in the situation.
“Through negotiation the Jedi maintain peace,” Yoda replied. “To start
a war, we do not intend.”
His continued calm only seemed to push the frantic Ask Aak over the
edge. “The debate is over!” he cried. “Now we need that clone army.”
Yoda closed his eyes slowly, pained by the weight of reason behind the
“If only Senator Amidala was here,” Mas Amedda reasoned.
Without hesitation, Jar Jar Binks stepped forward again. “Mesa mosto
Supreme Chancellor,” the Gungan said, squaring his sloping shoulders
as much as possible. “Mesa gusto pallos,” he said deferentially to all
the others. “Mesa proud to proposing the motion to give Yousa Honor
Attack of the Clones: Official Novelisation