Our dog Bailey is 12 years old, and our little dog Diego will be 10 in May. We feed them both Purina Pro Plan shredded. It comes in flavors of lamb and rice, beef and rice, and I believe chicken and rice. Both dogs really like it. The shredded part of the name means that part of the content is small and crunchy and part is soft and chewy. There is a senior blend as well.
Neither of our dogs has a sensitive stomach, but Bailey is prone to throwing up if she eats a large piece of something too fast. She eats much slower now and keeps it down nearly all the time.
We can only find Purina Pro Plan where we are at PetSmart. With a PetSmart perks card we can get it for about $35 for a 35 pound bag, which lasts us 4-5 weeks feeding 2 dogs. It may be cheaper and more available where you are.