omg thank you for putting this all together, do you know at least how far into gameplay you have to be until i could meet the construction workers?
I'm about 3 weeks into my current save and I occasionally run into them, getting catcalled by them is a random event that can happen when moving around town. Just know that to get the threesome scene with them you'll need at least 5 disinhibition and to encounter them several times! Walking back and forth between the Riverside Plaza and Yohimbe Street (where the River Rat) is how I usually find them.
FFM is certainly a thing possible in the swim practice scene, or if you're polyamorous and invite a couple female partners for a polycule hangout. For the other scenes I know the genders of the characters can be influenced by the player. Like at the very start you can choose to make the gender distribution of your world all/mostly female, and make your character a hetero guy so characters with predetermined genders are more likely to be female. Though that stuff is kind of "in theory" for me, as I usually play a bi female with even gender distribution :)