I think that Uncle Bud will chicken out and tell the Skreeps how to work the special machine because he gave a sort signal that let them know he's the real inventor. Not Dr. Shumway.
I think that if it were Jack he wouldn't trust the Skreeps. I also think Jack would trick them and say that he would set up the machine but instead he would sabotoge it.
One reason that Uncle Bud is similar to Jack is because the are both pretty dang smart, but they use they're brains different. For instance Uncle Bud uses his smarticals to build dangerous machines for mysterio cheerios like Mr.X. And Jack uses his smarts to soup some '53.