1) It's a little dated last I check, but the SCCM LearnPICU resources are an ok place to start.
2) Ask questions. This is your chance to get some experience with sick kids! Use your peds residents, the nurse practitioners, the fellows if they exist, and the attendings to answer your questions! And listen to the bedside nurses too, they are an invaluable resource.
3) It's okay to be selfish - focus on the kids that are there with DKA, asthma, trauma, status epilepticus, bronchiolitis and sepsis...the things you'll be expected to start management on in the ED. Focus your understanding on how kids are different than adults - like why is an insulin push in a type 1 diabetic dangerous but not in a type 2, or why does a virus (RSV) that only causes a cold in adults end up putting some infants on the oscillator in severe respiratory failure? It's not as useful for you to manage the post-op spinal fusions, the organ transplants, trach/vent kids, or mediastinal masses. Don't ignore these learning opportunities, but gently suggest to the other residents that you really want bread and butter patients. Help out others as much as possible and it shouldnt' be a problem.
4) At least act interested! As a PICU fellow, it was really frustrating to watch the EM residents just checkout during their month, disappear on rounds, not respond to nurses, or just generally act as an asshat while on the rotation. Yes, I know that when you're in the adult ED you get much more autonomy, yes I know that you have done months in the MICU, yes I recognize that you may have vacation this month and you're looking towards that instead of the patient in front of you. I really tried to be inclusive of the ED residents but at a certain point, if the attitude didn't respond positively, it wasn't worth my time and effort.