Dug foundations for new dorms, fixed bad plumbing, painted buildings and even their chicken coop with artwork, fixed leaking roof, did a variety of construction projects, made every meal etc.. none of the kids in our family group (roughly 50 of us in total) got any presents since all of our money went into the trip.
No complaints. In fact, the kids still talk about the experience as their favorite Christmas. They bonded together as cousins like we never expected. Many of them are now on missions, serving again.