Max,
I totally understand. I too was just diagnosed and my family is far away, and I can sympathize. I waited myself to tell them, knowing they would worry, especially since they can't see me to know I am carrying on business as usual. I waited until everything was confirmed before I told them, but news like this spreads fast, and the last thing you want is for them to hear about it from a well meaning friend passing on their support.
My parents were upset that I hadn't told them earlier, so it's a bit of a catch 22. I would tell them sooner rather than later, as they will want to support you. They will always worry (especially with you so far away) regardless of whether you are sick or healthy.
Best wishes to you, and if you need to talk, I'm a few steps ahead of you (I've had all my scans and my surgery is about 4 weeks away), but in the same boat.
Tina