My daughter is too young just yet, but I think my dad started taking me when I was about 6 or 7. I am the world's worst bowler though so when it is time to take the munchkin I think I'll let my wife teach her.
I started taking my niece and nephew at about 6 years old. They seem to really enjoy going with me. It gives us quality time and I am teaching them too, as I did not have anyone to teach me.
I think the first time I took them they were 3 or 4. The bowling alley had bumpers they put down for the little ones to protect them from gutter balls. Between that and the sodas and nachos, they had a great time.
We go bowling a lot. We like to do the moonlight bowling where they turn off the lights and only light up the lanes. That is cool! The kids love it too.