I'm sorry you had to go through that, and that your little guy wasn't feeling well. I hope he's feeling better now!!
I have a hard time with Roxie and my parents as well. When we visit their house, my dad insists the dog either stay outside or downstairs in the basement in her pen. He doesn't want her anywhere near food or furniture.
We actually don't bring her over there too much, unless it's a nice day and we can stay outside (like yesterday).