W1D1 done! :D And two noob questions inside.

Started yesterday with the treadmill routine, and I think I did okay - I'm not new to the treadmill, so I was comfortable with a 4mph speed for walking and 8mph for running (I know, I went against the FAQ, oops).

Since the gym will be closed on New Year's Day - and there will be some other holidays, for sure - can I switch from the treadmill-based program to the regular running outdoors one?

Does anyone also have suggestions for rest/off-day exercise routines? I've read the yoga post, and I'm also wondering if I can combine it with a circuit training routine (is that too high-impact?) or something.