You will be fine with a relay. Relays take a few milliseconds to operate and have lifetimes from maybe 100,000 operations to 10 million so you need to bear that in mind but for your application it will be fine. You might want to add something like this to drive the relay:
The 555 may drive the relay without an extra transistor - it depends on the relay current. The diode protects the transistor from the reverse voltage from the relay when it switches off.
Sorry for the brevity of my replies earlier - I was on my mobile phone so couldn't draw circuits!