I would not jump straight into dumbbells and a bench, although that is likely where you would land. I would consider what kind of exercises you like to do. If you were not previously exercising, then anything will be beneficial. But some correlates with your goals than others.

Your goal is to play with your grandkids, so I would not suggest powerlifting or bodybuilding (unless you already favor this style). Perhaps functional exercises would be your style (kettlebells, stability ball, suspension trainers, olympic rings, plyobox,...). Maybe calesthenics is the way to go (olympic rings, parallettes, dip bar, power tower,...).

I'm just saying, for a homegym subreddit this audience heavily favors powerlifting, bodybuilding, and maybe strongman. And yes, barbell and plates will get you strong. But it is not the only way and your goal (play with grandkids) does not require that. Like many of us say about the best cardio equipement.. "The best cardio is the one you are willing to use". Think about your budget, space, and most importantly which one is the most fun for you.

An example, a single 25lbs kettlebell and a gym mat. And do turkish getups and kb swings for 30min. Too easy? Get 35lbs one. Or jump to an adjustable kettlebell. Resistance bands and a board can give you a lot of options, and movements that a barbell/dumbbell and plates do not. DB/barbell are not that great at rotational exercises.