How great to be with the grandchildren! I am sure you are more than pooped when you arrive home, however you will not have any regrets and they will remember this time with you forever. It sounds like you are maximizing the jumping jacks etc and getting your body moving. Good for you.
On Monday, I completed a 5K with my daughter, who is in Florida, while I did mine in Minnesota. It was her 40th birthday and she did this through the Mn Vikings and their cause. It was great knowing that we were doing our best, even virtually. I walked the last two days in the cold rain, not real enjoyable however I needed out of the house. Today I drove to a small town and walked their park pathway, stopping at the skateboard runs and ran up and down them 10xs before I moved on. LOL
We all just need to move! Have a great evening and stay safe.