Guess if your traveling companions seriously object, then the best you could do is take pictures of your own food and just mention what they chose to have & whether they liked it or not (if you're doing a review.) If they look around the restaurants, I think they'd notice lots & lots of people taking picutres of food, restaurant decor, characters, etc. It's Disney, people are on vacation...cameras are everywhere.
My adult kids go with us often, and they looked askance at the picture taking at first...until I explained the reason I knew what was good at different restaurants and what dishes to avoid was because I read hundreds of reviews every year on my favorite forum...and that wouldn't be possible if people didn't take pictures & write extensive reviews for me. So I return the favor! After the first couple of restaurants, they all actively participate: staging their plate, showing off the dessert, etc. As well as give opinions on their food for my reviews.