Camping for Year 3

Robin Klein's Hating Alison Ashley is perhaps another possibility.

"The Nimbin" by Jenny Wagner. Also perhaps "Return of the Nimbin".  These are slightly longer 

Skating on Sand by Libby Gleeson
 Melanie and the Night Animal by Gillian Rubinstien
 Giant's Tooth
 Camping Out (Boys Rule Series)
 Croc Bait (Solo)
 The Great Outdoor Camping Trip by June Loves

Pilchards in tomato sauce is very lightweight but hilarious. Two boys go camping with limited food supplies as the title suggests
 by Alison Stewart, Random House, 1993