This isn't one of those Do-Over fantasy stories. It's a Do-Forward! Peg and Frank (40s) wake to find they have renewed bodies (20s) in present day LA. They need new living styles, moving north to Portland is the answer. In Oregon, they learn who caused their changes, including their runaway libidos!
My wife and I have a normal married life until a couple we have been friends with for a long time fall into hard times and we invite them to move into our basement apartment until they can get on their feet. The harmless flirting we enjoyed in the past moves on to the next level quickly and we all discover new sides to our mates.