Patco says it quite well.
"we go as fast as the slowest person"
We are also in our fifties and we found a great way to even things out. I ride often farther and faster, so when I tour with my wife. I carry almost everything. My wife carries her soft items in rear panniers. I carry tent, cooking gear, food, sleeping bags in a BOB trailer. If she wants it, I carry it. My days are shorter than if I was traveling alone, but I find pulling a ton leaves me happy at the end of the day even with the shorter distances.
In reality touring with my wife has changed my appreciation for touring. I go slower (we stay together the whole ride) and I see SO much more.
Have fun. I love touring with my wife, I hope we can do it for a long, long time