Please see my response under this topic for my opinion on some of your questions:
I went to an in-state university as an undergrad and I'm currently within the Astrophysical Sciences department at Princeton for grad school (though it is for theoretical plasma physics rather than straight astrophysics). I have to say I'm a little surprised that you are passing up some unnamed schools due to the inherent financial burden for undergrad, and yet Princeton still remains on your list (I believe undergraduate tuition here is on the order of 30,000 or more per year). To be honest, the fact that you're even thinking to ask these questions so early in the game says something (hopefully) about how much thought your son has put into his academic/career decisions. Most people don't think to ask about picking an *undergraduate* school for the particular researchers they may deal with. It's a good question for sure, a little preemptive, but good nonetheless. As an undergrad I'd have to say that physics is going to be difficult no matter where you go, so if you can afford to go to a more prestigious institution, why not? But don't think that just because you didn't get your bachelor's at some premier Ivy League or Tech school that you won't be able to get into a good research institution when it *really* counts--grad school. As I said in my other post, what is more important is that your son picks a school with a healthy research program in areas he *might* be interested in (I say "might" because academic tastes and preferences will likely change as you progress through undergrad....mine changed about 3 times before I nailed it down), and upon starting the program he should take every step to take advantage of the research and mentoring opportunities the school has to afford. An undergrad student from UVA with a few solid research projects under his/her belt, good GRE scores, a solid GPA with plenty of advanced coursework, and great rapport with his/her professors will likely beat out a middle-rung physics student from Princeton when it comes to applying to grad school...at least for physics (law, on the other hand, may be a completely different story...know any senators??).
So moral of the story- pick a place that fits the best into EVERY aspect of his life, not just the academic part. Princeton is beautiful, but my impression is that the grad students are much more laid back than the undergrads and there's not as much of a system of cliques, since us Ph.D. students are getting paid to be here whereas the typical Princeton undergrad is likely an upper-crust, well-to-do kid whose family can *afford* to put him into such an elite school. State schools are great places to obtain proper interpersonal social skills (which has benefited me immensely since I got to Princeton), and the larger state schools with large physics programs should have plenty of resources available as far as research is concerned.
If that didn't answer your questions, feel free to ask some more. However, perhaps your son should be the one asking some questions?