Easy, just switch 12V to the ignitor with a Songle 3A relay. Relay will survive around 100 000 operation cycles typical in this application, which will be a pretty big number of bangs. The typical ignitor is not exactly sensitive, it needs a minimum of 1A of current to ignite, and typically will drop 1V across it in the short time it takes to blow. You really want higher voltage than 1V to ignite them, especially as the long thin disposable leads are going to drop quite a bit of voltage in that ignition time. Serious pro ignitors use a 10-50uF capacitor charged to 200-400VDC and a really heavy duty switch to do a really high pulse of current to initiate a load of ignitors all in series with thin cord, so that all will detonate before the thin cable vanishes in the blast.