Loved reading your post! The changes you have made to your lifestyle should be celebrated! It was also inspiring to hear the impact your focus on healthy eating has had on your family. Sounds similar to my experience growing up. Dad was diagnosed with Type 1 diabetes and we as a family adopted a balanced, low fat, low GI healthy eating plan.
I really liked Chris' suggestion around having an open conversation if you can. I wouldn't worry about offending anyone, I know Dad has had to be uncompromising with what he is able to eat. His body can't process certain things, and it sounds as though you might be in a similar position.
When I cook for Dad, I really enjoy trying out new recipes. I recently tried out this Dark Chocolate Avocado Mousse recipe from Nutrition Stripped. If your hosts are open to it, perhaps you could try a new healthy recipe each time you catch up...Wholefoods Masterchef! Love a little bit of healthy competition! X Steph