Absolutely!!! It's done every day. :) In fact, I did it yesterday with my 11 year old sheltie. And it's easy too.
For inspiration, I teach competition dog agility. I had a student and her 9 year old Golden join my school. They were beginning students. This team worked hard, and the Golden learned hundreds of commands between the age of 9 and 14. She retired from competition agility at 14, but not before earning her Master's titles.
For exercise - both mental and physical - you might consider the Fitpaws peanut exercise ball. I'm writing a product review hub on it, but it's a great way to keep your dog in shape indoors. Agility competitors use the peanut, egg and donut to rehab their dogs and keep their dogs in competition fighting shape.
Whatever tricks you teach, have fun, and make it a great game for your dog. Congrats for wanting to keep him healthy and happy in his senior years!!!