Side note, it's better to learn to protect private property than to learn about confiscation. Forced sharing isn't sharing, it's like asking to share a car to someone you don't like. I understand that this might've been one of the thing that happen on top of all the other mess.

I think this was a good opportunity to explain to your daughter that not everyone can be friendly and how to deal with it (for her age). The threat also might not of been a good one since there might've been a lot of emotion going on at that point.

Now that the kid is going to your house, he should respect your house rules and that's where he will understand that you are serious. I would be less strict about small rule like cleaning up but more strict about bigger rule like "don't take other peoples toys away". This might be tricky since the parents are there and might cause trouble with your relationship. That's why you can see kids act better in daycare than in the house.

Personally, I don't try to do any discipline to other peoples kid. I use each opportunity to talk with my kids about the even that happen (sometime we talk about this for a few days). That way they'll be able to deal with it and understand it when it happens to them again in the future (especially if I'm not there).

Side note: it's better to learn to protect private property than to learn about confiscation. Forced sharing isn't sharing, it's like asking to share a car to someone you don't like. I understand that this might've been one of the thing that happen on top of all the other mess.

I think this was a good opportunity to explain to your daughter that not everyone can be friendly and how to deal with it (for her age). The threat also might not have been a good one since there might've been a lot of emotions involved at that point.

Now that the kid is going to your house, he should respect your house rules and that's where he will understand that you are serious. I would be less strict about a small rule like cleaning up but more strict about a bigger rule like "don't take other people's toys away". This might be tricky since the parents are there and might cause trouble with your relationship. That's why you can see kids act better in daycare than in the house.

Personally, I don't try to do any disciplining of other people's kids. I use each opportunity to talk with my kids about the event that happened (sometimes we talk about this for a few days). That way they'll be able to deal with it and understand it when it happens to them again in the future (especially if I'm not there).