The pricing seemed sort of complicated, with lots of packages and family discounts and so on. We got our tickets for the cave tour at a discount because we were at the Folk Center the day before and still had the receipt. As for time of year... I can onky say that we were there in early October and it was great... Not to many bugs, not too many people...
I just went after Labor day and they only offer the short tour or the Spelunking option until Memorial day. The longer discovery tour starts again in Memorial Day
I don't know of prices being any different for 15 and 12 year olds. As it was just my husband and I who took the Discovery Tour. There is a senior discounted price, I do know that, but don't know what it is. They have a website, which lists all their prices for each tour, and any discounts for individuals. As for best times? I can't think of a bad time, as its open year around. If you go during the summer; which is probably peak time, it might be a bit busier, but a certain time of year to tour is not really something of an issue. You're going down into a cavern, underground, where it's a balmy mid to high 50 degrees. So, yeah, even in the summer you're gonna need a light jacket, or sweater.
We enjoy going during Christmas season. They have caroling and its Awesome. The spring flows pretty much at a constant rate your round. Its beautiful in fall when leaves change.
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