The only virtual activities I've done have been asking volunteers to create cards for staff or having our crafters make blankets for palliative patients. I think something physical would be a lot of fun and a great way to engage.
Maybe you could kick it off in a newsletter and give out prizes for most steps taken in a day, longest distance walked over a specified timespan, etc. It would be great if you could do a drive through event and hand out step counters beforehand.