Question about Petzl Ouistiti

unlikely. I used it for my 4yo (at the time) daughter and for her it was set as small as it could go, and was not tight yet.
For a 2yo something like Edelried Fraggle in XXS would be a better fit.

That being said, this is a climbing harness, not a skiing harness. It has shoulder straps to make sure the child doesn't fall out if it flips upside-down on the climbing wall. I'm not sure how you would use it for skiing and I'm not sure if it would be a good fit, or whether you need the shoulder straps at all. Fraggle cannot be used without attaching a carabiner and rope in the front.