I have fished many of the trophy BC rivers, including the Kalum. The better fishing often occurs there on the earlier King run in late April and May. But it's also the more risky time to invest in a trip up there because snow melt has the river out a lot of the time. This year's snowpack could be a whopper too. All depends when the temps get warm enough to cause large melts. A rainless spring cold spell could put you into "Shang-gra-la" up there. Or it could darken the whole thing. Not just the Skeena River either. It's a spring syndrome for it's famous tribs and for the Kitimat R and Nass river tribs.
Noel used to run a section up high on the lower Kalum (the part of the river below the huge Kalum Lake) with his drift boat. You will catch more fish stacked up there but they will be more bronzed. Launching near Terrace where the Kalum runs into the huge Skeena and going up with a sled will get you into brighter fish, if not as many. Don't overlook backtrolling or anchor fishing the mainstem Skeena itself, in that area and many others. Backbounce or diver present the big '0' spin-n-glows with big well milking eggs clusters. If it has just enough water visibility you can fish downstream of the mouth of the Kalum and fish on both that run and also upriver trib's runs. Good luck.
The summer trip is a safer bet and there will be no shortage of great King fishing then on the Skeena and tribs. You might also look into a day or two saltwater fishing out of the coast port town of Prince Rupert. Should make a great combo of fresh and salt water fishing!
_________________________
the mind's eye is not always 20-20