I'm just wondering if I need to purchase a styrofome cooler to chilll my water bottles or if I could just slip them in the mini-bar like I normally do on vacations (outside of wdw).
No mini-bars in POR or Coronado. Another alternative to the syrofoam cooler is a collapsible cooler. They are quite reasonable at Walmart, come in different sizes and fit so nicely into luggage. I first used one of these on a cruise and it was invaluable. Have fun!
No, there aren't any minibars included at any of the moderates. You can rent one if you want, but I think it's around $10.60/day, so most people don't choose to.
It seems like CBR used to have them when it was the only non-deluxe resort, but they're gone now.