Any new vehicle is plenty safe for grandkids. Safety isn’t a real issue. Now, access and ease of installing and removing car seats and getting the kids in and out of said seats is an issue. I
Whether to buy a diesel version or not, that is an issue. If you must have a diesel motor, go for it. It will cost you more money over a gas motor, significantly more. The diesel will require more maintenance, and significantly more expensive maintenance. And if the diesel requires non warranty repairs someday, that will be a lot more expensive too.
Then there is the cost of fuel. The extra mpg you get is partly offset by the significantly higher cost per gallon of diesel in the US. So, if you get 20% better mpg and spend 20% more per gallon it is a wash. Don’t buy the diesel versions of these SUV’s without running the numbers to see if you will realize any real savings and benefits.
If you drive a lot of miles per year (like 20-30K) and trade the vehicles before the factory warranty expires then it could be a good deal. If you just drive 6000-8000 miles a year and want to keep the SUV for 10 years I don’t think the numbers support that decision.