Go when the day is really clear and you will be able to see for miles, if you have binoculars take them and see how far you can see, kids just love looking through them.
It is chalky like the rest of the Chiltern hills, apparently formed from fish bones. The ice age stopped to form the 'cliff' of the clappers.
The woods are a great place to explore, but are steep in places.
There are a few benches dotted about, and a big grassed area, that you can sit on for a picnic if you take a blanket. There is a footpath to the woods that you can wheel a buggy, and then explore the rest of the place on foot. There are no toilets at the site.
"Reputedly haunted, Sharpenhoe Clappers is a classic chalk escarpment and part of the Chilterns Area of Outstanding Natural Beauty. It is crowned with traces of an Iron Age hill-fort and an impressive beech wood."
There are a few walks in the area, here is one that I have found, that has lots of useful information:
Walk like the Clappers
Note that the pub in Sharpenhoe has closed down.
and there is also a pub right opposite.