Buildings 14,15 and 18 are the best for easy access to the main bldg (food court and pool) and the main bus stop.
We were in Bldg 17 and it wasn't a horrible walk, but if we didn't have a car (we used it just to go to the main bus stop) we would have had quite a hike with DS's 5 and 3.
There are just a few "smoking" bldgs, they'll tell you which at check in. Just remember that even those often house non smokers desiring the location. I don't know if our room was in a smoking bldg or not but I don't remember smelling smoke the entire time I was there, even while strolling along all the beautiful paths enroute to the pool and/or food court.