I tried to do what you said but when I got to the fishing trip there was no option to spend time with Bobby.The path to that relationship is crooked. First you cannot get a blowjob on the plane. Second you need to make the blue haired girl your girlfriend. Third you need to make all the "bro" choices with the brother. Then you have to respond positively when your girlfriend shows up with a strap-on. If you are on the right path there will be a scene where you can jerk him off on the couch. On the fishing trip you need to spend time with him rather than any of the other options and then go on the hike with him to the cave. Just like all the other encounters you can have in the cave, it ends in an embarrassing fashion.
Is there a specific choice I have to make?