My mom is a fairly non-observant woman who eats kosher-lite. In her case, this means only kosher meat, in restaurants she will eat fish/vegetarian, and she doesn't mix milk and meat. If a dish comes with shellfish/meat in it in a restaurant - she will ask if it can be made vegetarian or with fish, but she doesn't ask what kind of gelatin is in a dessert, if beef broth is used in a sauce, etc.
Recently, I went with my parents to an Indonesian restaurant where krupuk (the shrimp crackers) were on the table. At the time, I was about 90% they were the prawn crackers - but I didn't know if they were actually made with prawn or that was just the name.... Either way, my mom starts eating these and I didn't speak up to say "hey, these may have shellfish in them".
So I wonder what other people's "ethics" are in regards to disclosing to someone who's kosher or vegetarian that a dish might contain a "bad" product. That there might be dried shrimp in the pad thai, that the pumpkin soup might be made with chicken broth. I would never make my mom a dish with a product that I knows goes against her dietary choices - but if we're at a restaurant and she doesn't ask those kinds of questions, I'm happy not to tell her that she might want to ask.
What are other people's thoughts on when to disclose with people who have dietary restrictions? Not food allergies, but someone making a choice not eat xyz.