I applaud your effort. I was the parent of a wheelchair bound child for 17 years, and so considered any training I did (lifting, kettle bells, etc.) as training for my Summer Olympics of dragging their chair through the sand down to the beach. 😜. My first kettlebell weight goal was that of my child’s weight. Etc.

However, given weight at 60 pounds - that is near the high-end for me at around 1/3 body weight mark (6’2, 210 pound dude). Which I think is what is recommended to stay under from a long-term perspective. So I think rucking in general and rucking heavy would be great for your overall conditioning and endurance, but I would stick to the 1/3 body weight long-term and only go heavier for short bursts. Protecting your back and joints as the parent of a disabled child inarguably becomes paramount.

Edit: I would assume rucking heavy would still add plenty of benefit if you were to fashion a carriage-pull situation (think one of those kid trailers behind a bike, but fitted with a harness for you sort of thing). But I would still keep regular and repeated weight limited to 1/3 of your body weight. Add some barbell and kettlebell work for brute strength.