Cameron Boyce did not participate due to starring in his own Disney XD show, Gamer's Guide to Pretty Much Everything (2015). On Bunk'd, the reason for Luke's absence is because he's at summer school, though he does eventually make a guest appearance in two episodes.
The Ross kids had to go to summer camp as Jessie could not take care of them. In the last episode of Jessie (2011), Jessie began an acting career, though their mother Christina became a stay at home mom and could have cared for them.
The events of episodes from Jessie (2011) were never mentioned in any episodes of Bunk'd (2015), nor has Jessie ever been mentioned or seen.
The episodes "Camp Kiki-Slasher" and "Fog'd In" each opened with a warning stating that they were too scary. Younger viewers were advised to watch with a parent.