Two things...
When driving relays, be sure to get a relay with the shunt diode in it or plan to add a fast switching diode across the relay. The relay is an inductor which, in non technical terms, gives the current flowing through the relay some inertia. When you turn the power going to it off, that flowing current has to go somewhere, or it will pile up and create a negative high voltage spike than can damage the solid state driver. A diode installed in parallel with the relay with the correct polarity will block when the power is applied, and when the power is turned off allow the current to flow in a small loop at the relay until it stops. Think about pushing a loaded grocery cart. If there is no diode, you push the cart into the wall every time you turn off the relay... Eventually something will give...
How much current the relay needs depends on its size and construction. I think the bobcat servo controller currently has a 1k limiting resistor, which is only going to give you maybe 10ma per channel at the header. If you plan to push higher currents you may want add a little stick on heat sink to the chip...