Start with the Cake
You will need a green cake, Oreos, candy stones and candles.
Get your green cake and place the candy stones on it in a circle,
Now break all the Oreos into little tiny pieces and scatter them in the middle of the stones. Place the candles in it but put them right in so all you see is fire. There's a perfect campfire.
Make some camping themed invitations
You need a 4x8 green card and a yellow pen or crayon.
Bend the green card in half. Now on the front write in yellow crayon or pen the name of the child, their age they're going to be, the place it's going to take place and what party is it.
It should look like :
Come to ...... birthday party
Yellow stone land, Yorkshire
Inside write :
You are invited to ....... birthday party
Have green and brown pieces of paper dangling from the ceiling so it looks like tree branches are everywhere. Have a green table cloth.
* Hide lots of different types of plastic creepy crawlies around your house and tell the kids to find them when the can't find any more tell them to come back to you and count the bugs they have got the one with the most bugs gets a treat and is the winner.
*Hide tents around the house they have to find them if they want to sleep out in the garden.
Get lots of different things and make them look weird but wonderful, like getting hotdogs and put little ant sweets and call it the hot ant, or have burgers with spider sweets on and call it spider invaded burgers or make little buns and but a centipede and call it the centipede bun. You should get the idea.
Later on :
When its time you thought they went to bed just send them outside into their tents they won't go to sleep straight away they will stay awake but they should just drift off when they start getting tired.
Set them a challenge by seeing how long it takes them to get scared and run in.
Hope I helped and gave you some ideas, good look bye!