As national parks go it is okay. You pretty much just follow a path that is a little broken in some places but it is quite clear where you need to go, you do not need a guide. You can take a detor to a waterfall (steep unpaved path). World's End is a nice view of the valley below with a sheer drop down about 800 metres. Sri Lanka isn't under the cosh of heath & safety so they don't put up barriers etc, just assume that you are not an idiot and will be sensible. I would keep a close eye on kids.
Overall it is just too expensive for a 3-4 hour walk. Go early morning but if the weather is not great just don't bother as without the views, I just don't see the point.
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