First game = no real idea what I was doing. Started it for fun and ended up writing things all over the place trying to make a story out of thin air. So, I took what I learned and made (Hopefully) A much better game from the get go with a story planned way ahead of time and characters that have more depth to them overall.
I will say I have to agree with you about the first game writing being all over the place. I enjoyed the first game in the beginning because there were a few very hot scenes, but the more as it went on the more off the rails it went. By the time we got to the ending it felt like you were in a rush to just finish it off rather than have any sort of satisfying or natural conclusion.
This time around, I think your foundations are much stronger. Having Claire's sister living with them also makes more sense than having Jenni, since in the original it was never really seemed natural to have Jenni living with this couple.
The introduction to the swinging is much healthier with Claire first encouraging the MC to be with another women, and then letting the MC express interest in the opposite happening. That works much better than just "Because Claire's slutty friend encouraged her."