This is what I would highlight. Your previous care of critically ill patients. I would highlight your critical thinking skills, vent management, knowledge of abg's, inotropes, and vasopressors. Those things are much harder to "teach". It takes time to get those types of things and can only be learned from experience, which you have. The dosing is different in peds obvisiously, but if you know why dopa or epi works that to me is far more important. Your willingness to make such a huge change will be guided by how much you want to learn and how fast you want to do that. I think someone with critical care experience is a much better canidate than someone with no crit care experience at all but might have had some peds experience.
I would highlight those areas and maybe express your desire to learn new things and advance your nursing practice and your skill set and knowledge.