Good luck and I hope you find some. I’m on Crystal fairly often and I have caught 1 Atlantic Salmon through the ice this year. They are hard to come by. I’ve experienced they usually hit jigs rather than live bite through the ice.
Either way, I and friends have caught many more salmon on Crystal on open water. The bite through the ice is tough.
A great time to go is during the fall when they are making their rounds around the lake jumping like mad men. Some huge hookjaw browns also work their way into the frenzy. My largest Brown in CT was caught out of one of the salmon schools in the fall.
Regardless, the salmon bite at Crystal is better open water and they definitely will hit any time between spring and fall. If you put in a day on the lake drifting worms or shiners there is a good chance you will pull in a salmon.
I don’t have any advice on Kokanee but I hope this helps you and your son catch a salmon (or a few).