Hi Esther!
Welcome!
I'm not a gramma just yet, but I AM 55 and need to lose about 39 more pounds to reach my goal weight.
I've read Volumetrics, and it really works! You can eat so much more food if you eat the RIGHT KINDS of food! I LOVE food, so I want as much of it as I can eat for the lowest amount of calories.
Veggies are without a doubt your best bet! As you probably remember from the book, you can eat cups and cups of broccoli OR you can have this 1/2 of a bagel! Now, you KNOW which one will fill you up better!
As far as exercise goes, you MAY find out that as you lose more weight, your mobility will increase. My knees feel SOOOOO much better now that I've lost weight, and even my arthritis has tamed itself! Even if you can't exercise much, you can succeed at weight loss if you watch what you eat. Every bit of movement burns calories. My 95-year-old mom started lifting one and two-pound weights as she's sitting on the couch. My MIL does leg lifts in her bed. There are many ways to get moving without doing typical gym-type exercises.
I wish you much success! Come here often. There are wonderful people here!
Cheryl