I need some ideas for a cake. My daughter is 4 years old. She is going to be celebrating 3 years since she had a double lung transplant.

How about doing a cake with her doing all the things she loves to do that she wouldn't be able to if she hadn't gotten the transplant? For an older transplant kid you could do something with lungs but since she's only 4 I think that would be over her head. And congrats on her transplant and hope she is doing well. I work as a nurse in a children's hospital and we get quite a few transplant kids, both pre- and post-transplant. And they are some of the most awesome kids to work with :-)