Don,
Your very wise to test and preconsider the components of your rescue and alerting system.

I tested some flares a few years ago, that were 11 years old they lit off perfectly. These flares had been every where and been wet often. In signal flares, gun flares are best. More signal value and easier to fire, but that has to be offset with the loading and the weight. I use finger flares. In finger flares I like the fat ones better then the longer thin ones. If your travelling be sure not to carry them on the airplane

In adition to flares I carry smoke (light colors) and dye markers (for helitac and day time rescues) a flashing strobe a beacon a signal mirror. I know the last one sounds ancient but I have been signaled that a late arriving friend made the put in across the mouth of the Penobscot River from Owls head to Spectical island. I flashed him back we both gotthe message very clearly. over a distance of several miles. I have also tested it out on a friend in an airplane too. Its a remarkably alerting little piece of glass! I like the ones with the aiming hole in the center.

In the audio world a small canister air horn is good but in testing them I find the marine environment corrodes them and fills the aresol vent with crust , salt and corrosion. I test mine before I go out and I never keep one for more then a season. I also wash the vent with fresh water after every trip.The whistle is nice between folks sitting in the water, but no rescue boat will ever hear you.

In electronics: A VHF marine tuned radio With a water proof bag you can talk through is important. On trips into the Thules I occasionally bring an EIPRB. I don't out fit each boat with one, but to have one stowed on one boat is good for the whole group of paddlers. If you bring an EIPRB be sure to duct tape the switch in the off position. I have spent many nights hunting down a transmititng EIPRB that was not in any danger.

A good additional piece of equipment is a small stainless sheath knife. on your life vest. The marine environment is filled with fishing lines ropes netting etc. The is especaily true around the shoals we like to play in. Its good to be able to clear yourself quickly

Good luck with your safety system
!RUSS