Ragman wrote:If that were the case (speaker only speaking expressing gratitude on behalf of the family), then the speaker would have the option of saying "My family thanks you for the hospitality."
Your explanation unneccesarily clouds this issue. you need to think of the context of where this is being spoken. It is not a legal contract that is being drawn up here.
Adding context never clouds an issue, Ragman, for language doesn't exist in a vacuum.
In the initial example, I think it's certainly a conceivable option that the speaker wasn't there when the hospitality was extended and he/she is doing the thanking for the family for some reason, eg. they don't speak English.
Haven't you allowed as much by saying that the speaker could add,
"On behalf of myself and ... " ?