I've read that PEX will stretch a little and not break, but it won't do it too many times. I seem to remember three times as about the limit.
Definitely do more research. If PEX isn't the answer, that's a lot of money for nothing.
We don't let our basement get that cold, even if we're not here.
When I first came here, I rented, and the rental house had two valves, one to turn off the supply, and one at the lowest point to drain the pipes. That's probably the best idea.