You sound just like my kids. They have had a love of reading since early on.
My mother tricked me into loving reading... When I was little, she'd read to me every night before bed. ERB's Tarzan and Mars series, CS Lewis' "Out of the Silent Planes" series, and Jules Vern. We'd cuddle while she read, and she'd have me follow along. Eventually she'd have me "help" her read, and as I began to read more and more, eventually I wound up reading to her.
According to my private Hebrew Day School achievement tests, I was reading at a 12th grade level in 5th grade.
I still love reading, but rarely have time to read for pleasure: I spend far too much time reading technical and training manuals for work (network administration and management.)
But one day soon, I'm going to re-read Terry Brooks' "Sword of Shanara" trilogy (I have to admit, the MTV series made me want to re-visit those books!)
Mark