I don't often check this site but saw your question and thought I'd offer my perspective. I got my ACNP in 2011 and started work as an NP with a Neurosurgery department several months later at a Level 1 trauma center. I think ACNP is the way to go. I'm not sure which degree would be most useful with the impending "Consensus Model" though, you'll have to do some research.
In terms of my job, I round with the team in the mornings then see patients on the wards (wards only, no ICU) throughout the day, writing orders, following up consults and, primarily, trying to discharge people. About ~5% of my patient load are pediatrics on the wards.
Most of my colleagues work in the clinics with no, or very little, inpatient work. I only do inpatient.
If you were looking at an NP job with Neurosurgery, I'd expect full time Mon-Fri work, some clinic, some inpatient (ICU included possibly).
As for the OR, well, heh, I'd be astonished if you could be involved at all. Just doesn't seem likely although I have known PAs to be first assists in Ortho, vascular, etc.
Good luck, p