Thank everyone, A-Day weekend it is!
I agree with the posts above.
One thing to keep in mind, that once there, it can be cheaper to get a weekly rate (5 or more days) at some of the business focused hotels (suites) close by than just rooms for the weekend.
So we decided to include marchback, and thoroughly enjoyed it. Then toured up and down the hudson mid-week, could also have commuted into NYC. Then back for A-day, had lot's of room in the suite. And really enjoyed the time with DS.
Given the sunk cost of travel from CA, I'd sure plan on spending more time there than just R-day.
One other note: The gift shops, cadet store, USMA Museum, etc are all open and much less crowded after marchback than they will be A-day weekend.
Add in a guided bus or just self guided walking tour of USMA, and you can fill a day at USMA in addition to marchback.
A-day will be much more crowded, and your plebe will not want to spend time on post once you pick them up.
A-day weekend is also a great time to pick up the academic year items that your cadet wants: Fan, boodle box, school supplies, face soap, more non-issue underwear, etc. They won't know what they want/need at R-day, nor do you want to haul it around.
You should also try to work in a home game, ideally with other parents in a club tailgate..... I'm not a football guy, but we had a blast at our club sponsored tailgate/game, as did our cadet. made a weekend out of it, just a nice relaxing time and there is no place like USMA to watch a football game.
Our cadet was able to sit with us most of the game, and all the old grads surrounding us had a blast counting his pushups every time the knights scored.