Hi,

The voltage to turn the relay on will be 12 volt dc (max 50mA).

The load I'm trying to turn on is 120ac for a small coolant pump.
Then an SSR will be perfect, you don't need a contactor, the SSR does the job on its own. This is almost an identical purpose for which I bought
my SSR. I wanted to turn my coolant pump (240VAC) on and off, and my BoB signals 24V up to 50mA.

The SRR will work with any DC control voltage from 4VDC to 32VDC and under 20mA, so your 12V 50mA signal will be fine.
It can switch anywhere from 24VAC to 240VAC at up to 15A, so it will switch your coolant pump on and off no trouble.

So you don't need a contactor or a relay...just an SSR.

Craig