Definitely just watch with caution! Have a "safe place" for her to go, such as an expen, a room, etc. Kids and yorkies can get along well, with supervision and the right kids/dog! It can be a good learning experience for both. Jackson is great with most gentle kids, but he can be nervous around hyper active type kids. But what I usually do, to make it fun for both, is bring lots of treats. The 2 almost 3 year old should be old enough to throw a few treats the pups way. I usually have kids do tricks with him too, which they always find so funny, and he is most comfortable doing something he knows well.
I always love this video, of my little sister when she was 3.