My hubby and I were planning on also traveling to Canada / USA and have looked at nearly every policy available. Due to multiple myeloma damaging my husband's spine, we cannot get any travel insurance. Most of the polices here exclude any type of cancer. The only one we found that would possibly cover you is Chartis Travel Insurance.
We did find that Canada does cover travel insurance non-residents and will cover for pre-existing conditions as long as they are stable and no change in treatment for 4 months prior to travel. It only covers emergencies, but I figure enough to stabilize you and get you home.
From memory of reading the PDS, they will cover you in America but the majority (starting and finishing) is in Canada. Maybe you can make a big holiday as well as dropping your son off
Can you please let us know if you do manage to find someone to cover you?
Good luck, and I really hope you all manage to go.
