In theory! A distraction would certainly help draw Guards out of the palace, as they're under the impression Kathashun is trapped inside and can't possibly get out. Nothing is guaranteed and you may all get roughed up in the process, but with the plan you have laid out and enough people, there's no reason why the King can't be rescued. :)

And, as an additional bonus, if Julius and his squad do decide to free the King, it would certainly add a powerful ally to the people's side in creating peace in the city. Kathashun seems confident you all can do it, judging from his conversation through Jalin, and Jalin assures you all that Kathashun is not the type of person to put people in harm's way for his own benefit. If Kathashun is confident in your chances, then chances are, you will succeed.