Growing old, as the old saying goes, is a lot better than the alternative. Even with all of the aches and pains that come with aging, just the ability to look back on a life well lived contains its own kinds of rewards. Just ask the two older couples on the dance floor in Alwine van Heemstra’s uncertain “The Last Dance.” The legs are going and the coordination is failing, but there they are nonetheless, swaying to the soft romantic jazz music, clutching at each other for support and practically holding each other up. As they dance, a mellow stream of voice-overs from younger people relates the fears of separation, with its inevitable way of changing things forever, as well as their current intentions to stay united for all time. They’re exactly the sentiments the couples dancing might have expressed fifty years earlier. Like a cartoon that isn’t meant for kids, the poignant and bittersweet “The Last Dance” isn’t quite the sweet little film it appears to be on the surface. The subtle undercurrent of this unnerving short seems to be that although growing old may indeed be better than the alternative, by doing so, we tend to acquire some baggage along the way.