I think another act of service that was a big hit with the kids and the recipients was making little Christmas thank-you notes and tying them to Lindt truffles to hand out to the bus drivers. We ride the bus at least twice a day (to and from school) and the kids would fight over whose turn it was to give the treat. Some of the bus drivers didn't know what to say or do, but some of them were delighted. It was really fun.
Another service we did that delighted the kids was to go to McDonald's for dinner and pay for the car behind us in the drive-thru. There aren't a lot of drive-thrus in London so we don't have a lot of options, but it's always worth it. Even if we don't get to see the reaction of the people behind us, the reaction of the McDonald's employees is always entertaining.