I know a couple of people who have had bouncy castles, and it's gone down very well with kids and grown ups alike - we're looking into hiring for ours too!
One friend had some lovely photos of her and her groom on the castle, it was fab!
A couple of things to bear in mind - make sure the company has insurance, and if you are letting kids use it, make sure that either the company will provide a person to watch over them, or make it clear that parents have to stay with their kids - most companies will tell you about this anyway.
If you decide not to go for this, the wedding I went to on the weekend had photoboards - the ones where you put your face through, like at the beach!
We're also looking at a giant jenga, connect four, swingball and a croquet set.
Hope this helps! X