Chicago.
Tour Boston so it's not just staying in the city but explore the NE area for a few days.
I personally would not do CA in 6 days and going west as it's a longer flight. I like more time in CA to see different places personally. However we really really loved Santa Fe. And no, it's great weather

we did end of June and really loved it. One of my favorite places. Younger the outdoors but there's some serious money there so the food and shopping is amazing. One of the best kept secrets I think - people choose SD - I think Santa Fe is like 10000000x more fun and interesting in every possible way. I find SD a much more vanilla place. It's beautiful but I wouldn't spend a wk there. Id live there though

the difference is that it's beautiful so I'd enjoy it everyday but in terms of stuff to do - I just don't think it's all that for an actual holiday.