My girl is just like this. The cuteness and the dignity never seem to clash! When I adopted her I was told not to play too wildly or wrestle with her like other dogs because she could become "dangerous" if excited. Well, that quickly proved to be nonsense. Trust is always a 2-way street. A wolf will trust you as much as you trust her. Trust is demonstrated by allowing oneself to be vulnerable. For example, wolves, like many dogs, are very mouthy. They will obsessively take your arm or hand into their jaws and squeeze. It's a way of gauging and establishing trust.

A sane animal will never cause pain for no reason, out of the blue. Wolves are great communicators so it's easy to distinguish a playful mood from a serious one. Another easy way to show trust is to lay on one's back and rest near the wolf. The extent you can trust is the extent you will be trusted. This probably goes for all relationships, not just with wolves.