If you're ever worried about being too old, don't be. JonnyBuz is like 26 or something and he's coming for 2 sessions, and we have people who are in their 60s every year. There will be plenty of kids your age there, so don't worry about that.
Baggage fees depend on the airline. Google is the place for that.
As far as summiting Hood goes, it's sustained steep snow travel above the bergschrund, and possibly also ice/hard snow in the Pearly Gates, so you'd need to bring an ice axe and know self-arrest at the very least. I'm not sure if it's skiable from the very top, but you can almost certainly ski from below the bergschrund.
I'm actually going to start investigating up there this summer with one of the other counselors. Probably going to bring ice axes and see how far we can safely get. If there's a bootpack it may be doable without protection.
As far as you doing it as a camper, as long as someone on staff also has the gear and know-how and is willing to go, something could potentially be worked out. It's something I'd be interested in doing actually. Crate hike is certainly a possibility, and will get you close to 10000ft.