Bearanne, our unit sees a significant number of kids following brain tumor resections; there really is no typical patient, but I can maybe give you a snapshot of what to expect. It's possible your son may require mechanical ventilation for a short time following his surgery. He could also have either an intracranial pressure monitoring device or an external ventricular drain (which can also be transduced), as well as an arterial line in place.
He will have a minimum of two large bore IVs in and will be at risk for both SIADH and DI, in the first 72 hours or so post-op, so will probably have a foley. Expect frequent neurovitals for the first 72 hours as well. There will be a lot of what looks like busy work around the bedside for awhile, but it is all essential to his well-being. There is a risk of postoperative seizures so you may see him started on prophyllaxis, as well as antibiotics for as long as any invasive devices in the head remain. He will be groggy and disoriented at first; that should gradually clear. His movement will be restricted by his monitoring devices and possibly restraints, if he's too wild. Then there are some kids who come out extubated, and talking, who only require ICU for a day or two before they are on the road home.
Best of luck, and make use of your best resource, the bedside nurse!!