This is indeed a spectacularly bad film, but it is the rare kind of badness that is endlessly, jaw-droppingly entertaining! I want to add to the other comments on this film.
The "rock band" on the plane look like three skinny drunks from casual labor wearing bad wigs.
Watch for the severe continuity problem with the kid's stuffed tiger: it turns into a lion, a leopard and back again; it's filthy or clean depending on the shot.
*SPOILER! The stuffed tiger turns into a real animal to save the kid (and the writers)!
The sight of little Jimmy floating down the Amazon in a coffin, clutching his stuffed tiger and squalling away will stick permanently in your memory.
Listen for one of the most inept sound effects ever: late in the story when the priest is setting out to find Jimmy, the guide demands his monk's robes as payment-the priest drops on one knee in a moment of resigned contemplation and there is the sound of a bell, not the deep "BONNNNG" of a church bell, but the "ding" of a bell from a boxing match!
This is an absolute hoot to watch.