I've taken both Charlie and Kelan on one-on-one trips and I'll confirm that traveling with a single grandchild for a week is life-changing. In a good way. We bond, get to know each other without parents or siblings to distract. We take one another's measure. We learn how to be a twosome. I recommend it.
So these lunches are a spin off of sorts - a change to recalibrate unique friendships. I love these two grandsons of mine.