FourBases,
A couple thoughts.....
Please let us know how the official visit goes. Unfortunetly, your son only has 48 hours on campus to get information and a "vibe". Whoever your son gets matched up with as a host, try to get as much info as possible about your son's major, baseball team, and social life.
I would follow up with goosegg on his offer to help you. Feel free to PM me as well if you need to get into specific private matters. Goosegg's son's recruiting path was very different from my son's, and the guy knows his stuff. Getting many different perspectives and opinions could help you with your effort.
I agree with 9and7Dad that 2015 athletic recruits are done for top tier academic D1s schools like Vandy, UVA, Duke, and others. So, that ship has sailed.
Lastly, I think your son should go into this weekend prepared to respond to an Ivy coach who may be offering a slot on the team. My sense of things is your son may be a recruit the Coach has already convinced Admissions or is going to have to convince Admissions. Just because a pre-read comes back "thumbs up" or an OV is offered, it is still not a 100% guarantee of an offer or admission to the school. You've got to go through the Ivy gauntlet one step at a time. Trust me, I've heard of many "squirrely" stuff that has happened to folks in this process. So, the Coach may have stuck his neck out a little bit to get your son based on contingencies (ie..retake SAT). The Coach will most likely want an answer soon. I'm not saying you should say "yes" or "no" to the offer which may include those contingencies. I'm saying don't be surprised with an offer and you may want to rehearse a response with your son.
Good luck.