Here's a couple of other things you could try to make the site more useful / sticky to visitors.
Try and use some kind of voting / comment system where visitors can rate each park. You could split it into something like quality of rides, length of queues, value for money etc. Give users buttons to click and a chance to interact rather than just read pages and not return.
Add local weather for each park. Link to a weather site such as BBC weather with each page having the postcode automatically set.
Same applies for the google maps. Rather than show the map of the locality use one of the google gadgets which has the postcode for the attraction set and the user is prompted to enter their start postcode.
This is much better than just showing the chart or the 'click for directions'. Here's an example from a different site:

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