Get a GOOD alarm and use it. Train your kids, if old enough, when they hear the alarm, run to daddy's bedroom
I would not count on kids, even teenagers waking consistantly to an alarm. A few months ago a fireman was telling me about kids sleeping through fire alarms and how they are now coming out with smoke detectors that record a parents voice yelling at their kids to wake up. He said these new detectors were much more efffective.
I tested this one night with my younger kids and 13 year old nephew. Neither the smoke alarm or security alarm woke them up...just something to consider.