Though I have been in it many times, I just cannot recall exactly what the heights are, but I believe it runs from 3 feet to 8 feet. From recall, the low end should be fine for a 5 year old.
One consolation is that the BWV pool has lifegaurds. I find this little bit of security for my children pleaseing to me. Not all DVC resort pools have lifegaurds.
I think the pool is 2 1/2 to 5 feet. I don't believe that it goes over your head (well, if you're an average sized adult). My 3 year-old daughter was able to stand in places.