Hi David,
Depending on your wife's condition, check out if a recumbent bike/trike would let he ride in less pain or provide more support.

In my house, we got our 2 cats and 2 dogs at pretty much the same time. We didn't realize the consequences of this was they would all get old at the same time. It has been a tough couple of years for us pet wise. I feel your pain, but I'm glad you got a new puppy. Get a pet trailer and take the dogs with you.
Cheers, Charles