Five years may not seem a "wide variation," but one grandchild starts kindergarten next year and the other is in fourth grade. When we're babysitting, I'd like to do something with them that both will enjoy, instead of just leaving them on opposite ends of a couch with their faces hidden by iPads.
Bonus if it is somewhat educational. “Go fish” seems like it might work, but the younger might find it difficult to know what to ask for.
UPDATE: “Go Fish” was kind of fun, but he's still too young to hide his cards from me or make good choices on what to ask for. “Concentration” he also enjoyed, but again, no concept of strategy yet. His older sister wasn’t here this time.
I was a teacher for a while, so I have some ability to evaluate things, but not so good at finding games/activities to evaluate.