Buying some travel snacks like mini packs of cheese, a rotisserie chicken, maybe some peppers, etc. and packing them in a cooler is a good start. As far as restaurants go, steak and salad or another meat (ask for no sauces) or caesar salad can be an easy alternative. Even Italian restaurants can be negotiated with careful choices. I know it is hard in family situations sometimes. I tend to hang with the kids instead of the adults when it gets too intense. They are usually playing and keep me more active anyway.
And you can invite others to take a walk, volunteer to run to the store, anything to break the stress if need be.