If you are in/around Toronto (guessing), then the nice little electronics shop on Queen St West, just east of Active Surplus, has nifty little hybrid packages they call "solid state relays", from 3 to 40 amps capacity. These have built-in opto-isolators, trigger on <1ma or <7.5ma (depends on model) over a wide range of DC voltages, and work nicely for this kind of stuff. Some are for AC loads, some are for DC. Prices from $5.40 to $24.50.

Cheers