Trying to make a weight loss meal plan for my 50+ yo parents. Is there anything I should watch out for?

Not sure if this is the right place for this, but it seemed like the most appropriate subreddit. LMK if there's somewhere else I should be posting this.

Back story: Both my parents are in their 50s. I was recently texting with my mom and she said something along the lines of "I'm so fat I don't even want to think about it" semi-jokingly, but not really. Obviously, it breaks my heart to hear her say something like that, so I wanted to put my food and nutrition knowledge to use and help make a healthy weight loss meal plan for them with ideas and recipes of things they should be eating every day.

I recently went through an 'unhappy weight' stage where I gained ~10 pounds, but then lost it all within a month by following a modified version of the 4 hour body. I want to create something similar for my parents that is mostly slow-carb, but I don't know if food components need to be different for someone 50+ yo vs someone in their early 20s. Is there anything I should take note of when making this for them (e.g. certain nutrients they need, more carbs, etc)? Or can I pretty much just make a meal plan that reflects the same types of things I eat?

For context, my parents live in a tiny southern town, so they don't always have access to certain types of ingredients or foods. They live a mostly sedentary lifestyle, though my mom walks on the treadmill or goes to step aerobics almost every day, and my dad plays golf often. Neither of them are obese by any means, but I'd definitely like to see them eat better and feel better so they can live longer and be happier. Also, my mom had breast cancer about 5 years ago and went through chemo/radiation, so not sure if that would affect the types of foods she can/can't eat when altering her diet.

Sorry, that was so long! Thanks in advance for the help!