Hi David - here's what to do:
When you said that you have all characters in the tent - that is wrong. Loof and Quookie shoud be in the back area (Peegues section) once all the keys have been collected. Stinky should have build bridges with the boxes to Loof and Quookies starting points enabling them to get through to the exit area. Only Stinky exits through the back of the tent.
Then have Loof and Quookie stand in the little nooks as in the screenshot. First use Peegue to push the two pink boulders left and right. Then use Peegue to push the blue boulders infront of Loof and Quookie - they then push the blue boulders up into the water. Then have Peegue stand back in the centre (his starting position) and use Loof and Quookie to push the green boulders up and Peegue pushes them left and right into the water! Then you can get the bonus coins and exit!
Sorry the arrows are crap - but I hope you can follow the picture.
You can do it!

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