"Scout" usually doesn't equal "wise" until they're much older.
So very true!
That said, regarding size, I am pretty set on the 2 man. In most cases I plan on using the tent alone. At Scout camps my son is paired with another Scout, not with me, and on any backpacking trips (only one planned so far for this year) the plan is not to share tents (so far at least!).
That's not to say there will not be occasional trips where I share the tent (I have been planning 1-on-1 weekends with my kids for example), but I haven't been able to justify moving up to the 3 man because of the amount of solo use I am currently anticipating.