Hey there,
I'm not a children's nurse, or planning to study that course - I'm a support worker on a mental health unit and want to go and do MH nursing, I'm also a graduate and wanted to give my two cents.
The first thing that comes to mind is why not apply? If you get to summer next year and feel your not ready to start the training then you could always defer your place for a year. I'd also advise against doing a different degree first (I think you mentioned that) - all that means is when you come round to doing your nurse training you won't get student finance and (apart from tuition fees) won't get much in the way of funding - I've had to save around £15,000 to do my nurse training and will have to work all three years of the course.
The last thing I'd mention is something I've heard from current students, nurses at work - but also a nursing lecturer I was talking to recently - at the moment we get good funding from the NHS (especially for tuition fees), no one know's how long that's going to continue.
I hope you do apply to do your training - it's a fab career to be involved in and something everyone I know loves - but whatever you decide, good luck!