While midlevel providers work in adult ICU settings with varying degrees of independence, I'm currently unaware of any Pediatric ICU's that grant the same level of autonomy. There is always very close supervision in every PICU I've worked at, with the APN's and PA's mostly functioning like residents. Where I did my PICU fellowship, one of the APN's who could actually claim to be one of the very first NP's hired in the PICU back in the 80's still had to run things through the fellow.
For the OP...it all depends on you and your preferences. I think we are a very long ways away from DNP's being able to practice with complete autonomy in the PICU except in the smallest, lowest acuity, PICU's that ship any truly sick patients out to bigger centers. Talking 4-6 beds that mainly deal with bronchiolitis, easy DKA, and simple asthma exacerbations, in cities that are limited in size (100-300k). If that autonomy is a pressing issue for you, then you'll need to go the MD route regardless. If autonomy isn't that big of deal, but you want to live in bigger cities, and/or have a broader scope of pathology, then either MD or NP can work out.
Regardless of your path, they will still require a significant amount of training. MD is going to be 4+ years of undergrad, 4 years of med school, 3 years of Peds residency, and 3 years Peds CCM fellowship. Becoming an NP is going to be 4+ years of undergrad, at least a year as a bedside nurse, 2-3 years of NP school (most places are requiring their Peds ICU NP's to have their pediatric acute care designation which is adds additional time to peds primary care coursework), and then a typically 4-6 month orientation period before being on your own with just an MD in the background). However, because of the nature of the PICU and the degree of patient complexity, people are going to view you more favorably if you have 3-5 years of bedside RN experience in the PICU including time as a Charge Nurse. The best NP's I've worked with in the PICU were excellent bedside nurses for a number of years before they went on to NP school. The PA's I've worked with in the PICU generally don't have the same background but were exceptional - at the top of their class with glowing LOR's, and who had done rotations while students with the PICU's that ultimately ended up hiring them so they were known entities.
