I went there a few years ago - it was full of diggers!
You can pay for a load of tokens and use them on the various different diggers - bigger diggers require more tokens etc.
There are different activities to do with the diggers - hook ducks out of a lake, hunt for treasure, or dig holes!
There were other bits and bobs to do too - a play area, Land-Rover ride, gift shop and digger-based rides.
It was a good day out but budget around a tenner each (or more) for tokens if you want lots of digger-related fun!