One of the clowns swung a pail of paper scraps at Jenny, causing her to scream.
The underlined phrase "exploring the surrounding area" means that the speaker and Hexa were actively searching and examining the area around their campsite. They were likely looking for interesting things to see or do, or perhaps they were trying to familiarize themselves with their surroundings for safety purposes. This phrase suggests that they were actively engaged in discovering and experiencing the environment around them.
Jenny's favorite act was the clown's act, as mentioned in the passage. She and her brother enjoyed watching the clowns with their painted faces and baggy costumes. One of the clowns swung a pail at Jenny, which caused her to scream. This action made scraps of paper fly out of the pail and the audience laughed. Therefore, the last performance that Jenny saw was the clown's act.