I'm most relieved to hear it. Perhaps in future you might avoid implying that trafficking and modern slavery are exclusively international issues? The charity Unseen gives very good talks, and their speakers make sure to include local data. It's a live issue in 21st century Britain, and it happens all around us, because people don't recognise the signs as their preconceptions of what forced labour looks like get in the way.
Assuming for the moment that everyone in your friends' situation is truly happy, exactly what percentage of unhappy outcomes are you willing to turn a blind eye to, for that one family's happiness? How many people's health and wellbeing can be destroyed for theirs?
Incidentally, I am very well-acquainted with the results of a situation with amazing parallels, also involving alternative parents who lived in 80s squats. The eventual adoptive parents who brought my school-friend up gave the child an amazing upbringing. Nevertheless, in retrospect, I think the signs are there that they suffered consequences of disrupted attachment in infancy, and it's led on to lifelong mental health issues in their adult life. Will any of the parents and other adults involved admit the link? Never in a month of Sundays. They and their friends from the time are rather biased, aren't they?
Also, I must say, I am perplexed by your reply to NotBadConsidering. You are a regular user on this board, so why post a variant on "bad things happen, so why shouldn't we knowingly and deliberately create avoidable situations with increased risks x, y and z, if it will make some people happy?"
Have you not seen how we respond to trans activists posting, "women get raped any way, so we might as well let men access areas where women are undressed or vulnerable, as it will make the men happy"? Did you envisage a different result?