Teaching an old new tricks is entirely possible. The trick is this. Don't ask him to do anything his body can't handle. Michael Hayward explains here that it's all about mental stimulation. And old dogs need that as much as young pups.
Ever looked across the park at Betty and her dog Reg, where he's all bushy tailed, performing a double front flip with sideways glance? Betty takes it in her stride and walks off in the knowledge that everyone has seen the performance. And have you ever felt that a) what a show off Betty is, and b) that your dog could do that, if it wanted to?
So there you have it, a few nifty tricks to show off to Betty and Reg. Don't forget to reward your dog for their patience as well, because sometimes they won't know what on earth you are trying to make them do. Good Luck!