I am also not in Holmfirth, but not far either. Its a toss use whether Holmfirth or Penistone is my nearest town.
Our DC are 6 and 9. We go to Holmfirth quite a lot, and have friends there. The DC ride with Holmfirth Cycling Club and use the tennis club at Thongsbridge (on the edge of Holmfirth). As the PP said, lots of stuff going on, lots of useful shops, easy access to both the Peak District and Huddersfield, and Sheffield and Manchester a little further afield. Also excellent gigs at the Picturedrome! There are always posters around for orchestras, choirs, music groups, sports groups, walking groups, hobby clubs, U3A, WI etc.
Holmfirth High is very good.
The only downsides -
1 - It has the coldest swimming pool in the world. (FACT!)
2 - The train station is actually a couple of miles away in Brockholes.
I plan to retire to one of the hill villages above "The Firth" , but at the moment, its just a little bit too far to work.