There's turtleback zoo in West Orange. Could swing by and wave at the Prudential center on your way into the ironbound afterward for some Portuguese food as well.

Diggerland is in south jersey, but if I know anything about Ontario license plates, you're heading down last AC, so it'd be out of the way to head west. Not sure what kind of time you'll be spending.

I forgot to add, I've done and will be doing drive from Jersey to Montreal a bunch. Once you exit Jersey, either from here to Montreal or to Toronto or Ottawa, there's very little to do. Maybe from Ottawa for Niagara you can visit the Finger Lakes, but for an 8 year old, it won't be too fun. Straight through from Niagara is about 6-7h. And upstate NY cops are the worst. So not a great ride, is what I'm saying. Flying, however, to Montreal, for example, you end up hardly saving time over driving, if you just chug through the trip.