Walkthrough: play the goddamn game. Talk with characters at various points of the day, especially during the dinner. Bring them out with you on the gathering mission. Build the items on the bench, etc. Just play the damn game.
The sister: visit the bathroom in the main camp lodge. Repeat until vaginal sex.
The counselor/aunt: get injured while she's in your party, repeat until blowjob.
Mother: repair water heating unit for bath scene. Repeat bath scene until handjob. Fix television for makeout scene. Gather more movies in the camp (random drop) for handjob scene.