Driving multiple optoisolators, with fault detection
simulate this circuit &ndash; Schematic created using CircuitLab

This is the best i could come up with. All the values are aproximate. The udn2987 is an 8 output driver chip with over current protection. Two of these will fill your needs. At the output R1 drops the voltage to 5v before the opto. 

Here is the idea. When the opto is connected and off it will drop the voltage at the sense point to low. If the opto is disconnected (open) the sense point will be driven high by R3. If the opto is off and sense is high this is a fault condition.

If there is a short on any channel the udn2987 will assert its fault pin. If the fault pin is asserted then there is a fault. 

This way you can drive and sense 16 channels with 34 pins. 

The only problem is the udn2987 requires a minimum of 7v. Better ICs may be available.