Dogs, no matter what their size, have a natural instinct to walk. I think all dogs need daily, or at least weekly walks. My friend (who is here on yt) has two 5 lb yorkies who walk with her for over 4 miles. So they can definitely keep up. Just be alert.
Walking around the house is not the same because it's nothing new. Walking is as mental as it is physical. New sights, new smells, etc are all primal instincts of a dog. They were born to walk and follow. Many people will say "he has this huge backyard - he doesn't need walks!" but it's simply not true. Sure, they may get a lot of exercise but it doesn't fulfill their needs. That's just my take on it!