It's been a good 20 years since I visited the caves and I can't say as for the extra money they've necessarily enhanced the experience too much. The audio guides for Goughs cave are great but it does rather get in the way of it being a family experience if you're all stood there with the audio guide held up to your ear.
The Crystal Quest we'd bigged up hugely with our daughter but it was very disappointing. It was over in a matter of minutes and consisted of nothing more than plastic characters and a bit of smoke.
The museum was very informative but beware if you have very little children. Around the corner towards the end where the cannibalism exhibit is there is a huge and scary dismembered head rotating on a pole. There is no advance warning of this and it scared the life out of our 4.5 year old.
We did appreciate the 10 year time span of the entry ticket as we chose not to use the open top bus due to the weather.
Overall, it's not good value for money compared with e.g. Wookey Hole. If I had paid full price for my daughter to get in too (thankfully she was under 5 and so went free) I'd have been very disappointed as to what you get for the money.
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