Helping in normal daily activities, even if those daily activities to include some hard labor = acceptable to me, as long as it doesn't interfere with other responsibilities - homework, boy scout/tae kwon do activities, etc..
Having an activity scheduled to take advantage of the fact that a kid is there to provide free labor = not so much, especially if the activity takes more than say, 25% of the time the kid is visiting. So I don't mind a case of 'ooh, look, we've got an extra hand, let's spend a few minutes seeing if we can't move that couch' instances, but 'hey, look, we've got an extra hand, let's remodel the living room' is a different story.
I guess my view comes down to 'kids are people too, and deserve respect' viewpoint. If you'd be uncomfortable asking a visiting adult to pitch in, it's wrong to expect a visiting child to do the tasks. I used to hate going to family gatherings because I'd be expected to watch all the other kids, and this seems on the surface to just be a variation of that. I think the kid should have been asked, and there should have been a reward attached to saying 'yes', even if that reward is nothing more than 'getting to visit in the first place'.