ISBoxer and Innerspace will accomplish seamless mouse broadcasting across your 3 clients. It used to be hard,

[Innerspace] Innerspace Windowsnapper, Repeater, and a little extra sumptin sumptin and now it's a lot easier

[Innerspace] ISBoxer Toolkit - Getting up and Running With Innerspace...

That said, if you need any help getting it setup you can ask here or in the IRC channel, people are always there to help.