Festival Fever

So we're off to the Greenman Festival in about six weeks time.
I'm starting to get very excited.
But one thing I struggle with at festivals is what to wear.
I see pictures of girls and ladies wearing hotpants and wellies and they look great.
But at nearly 40 I don't really feel that I could pull off that kind of look (or more importantly inflict my  legs on the world!).
So what does a late thirtysomething wear to these things?
I've got jeans but could really use suggestions for trousers.
I've got hoodies and sunhats.
But what about tops? I like smock tops/tunics. But I need something that won't crumple and look un-ironed!
I need help please!
I have fallen in love with a couple of these neon pink influenced pieces.
Mink pac-a-parka from Topshop. (which I've purchased a bargain at £20).
Wellingtons from Hunter.
Any suggestions? x