As if the past couple of weeks haven't been enough of a rollercoaster ride, Michael Jackson's kids hit up Six Flags Magic Mountain this weekend with one of their newly appointed co-guardians.

No, it wasn't 82-year-old Katherine Jackson. This time, TJ got the nod.

Paris, Blanket and a sleeveless Prince spent their Saturday with the fun co-guardian -- hittin' up all the crazy rides at the theme park ... including "Revolution" ... the first rollercoaster ever built with a loop.

The Jacksons love suspense.