Children with abdominal aortic aneurysms (AAA)

My 10 year old son was recently diagnosed with a 1cm saccular abdominal aortic aneurysm. The diagnosis came as a surprise - it showed up during an abdominal ultrasound being done for another purpose. The vascular surgeon has decided to monitor the aneurysm for changes, with the goal to delay surgery until he is fully grown. Until then, he’s been advised to avoid contact sports. I’m a little stuck on where to draw the line though. He obviously will not be involved in hockey or football, but what about participation in other activities that have an impact risk, like tobogganing or snowboarding? As a parent, I want to make sure that I’m being appropriately cautious without overly restricting his participation in activities that he enjoys.