What can we do today at my friends house?

I'm 12 and in 7th grade. My friend Kelsey said I could come over at 1pm and Jess is going over at 1pm to we are staying unitill 7-8pm. Anyways, we are going swimming and ding dong ditching and prank calling.. she said to bring a hoodie and a bikini, what else should i bring? Today's high is 83 and sunny. She has a inground 7 ft deep pool and inground hottub and a huge house alomst mansion but its not a mansion but its not a house, theres also a park by her house. Any ideas?? Help!!!? BTW, Kelsey isnt girly she's skateboarding type, Jess and I are girly but not totally.