Should I upgrade from Nikon D500 to D810 for family photography?

I'm currently shooting with a Nikon D500 and generally happy with the results for my family and kids photography. The autofocus is fantastic and I rarely miss a shot of kids running around. Most photos turn out great, but occasionally I find myself wanting more resolution for cropping or just zooming in to see some details. I'm considering the D810 for its higher megapixel count, but wonder if it's worth the investment given that I'm already satisfied with most aspects of my D500.

For those who've made a similar switch or own both cameras - would you say the resolution bump justifies the cost for primarily family photography? I've never owned a FF camera before, had a D3300 and switched to D500 for better autofocus, and I loved its handling, body form, and weight. I'm not sure if FF camera can produce better IQ with the right lens. Currently, I have a 16-80mm 2.8-4.0, 50mm 1.8, and 70-300 AF-P DX lens. I plan to keep my D500 for taking photos of kids playing, and the new camera is for portrait and family photos. My budget is $1,000 for the camera, and plan to use the existing 50mm 1.8 to see how good the photos are before buying new lens in the future.