How hard a course can be is a bit of a subjective thing tbh. Saying field X is harder than field Y is a load of rubbish IMO. It will depend on the student and their interest in a specific area as to whether they find it hard or easy, as a lot of motivation for learning in adults is driven by their interest in a topic. I'm adult nurse trained, I have a strong interest in critical care nursing (good job as it's been what I do for over a decade) and I would probably find the concepts explored in mental health nursing much more challenging than some of the A&P stuff that I know at depth because of where my interests lie.
You've been given a place on the course of your choice which means the admissions tutors have the opinion you have the ability to get through the course. You sound like you are very interested in childrens nursing and that will be half the battle as you'll be engaged in your learning. There's loads of support in the university to help you get through the course, make sure you access it and you'll get along fine.