Good Braking on a tandem is a must.
What year is your machine?
Back in the day most owners fitted a drag brake on the rear wheel. (If the left hand side of the hub is threaded for one .)
When we bought our tandem back in 2000 I found cantilever brakes lacked stopping power on desents . They were Campagnolo cantilevers. After a scary ride in the peak district I fitted magrua hydraulic rim brakes which sorted out the stopping.
I have a Campagnolo rear tandem hub spare, which is threaded for fitting a drag brake . 130mm wide.
If you go for normal brakes, use dual pivots . They will improve stopping power. You will probably need nut fitting ones . Is the rear bridge drilled ?
A drag brake is a must on long desents. Rims can get very hot .