Neat.yes trying to plan trip ideas with family partner realities isn't always easy. I have adult niece and nephew in London, so could fly there and visit, and then bike up to northern Scotland and see sister and mother. Or reverse, fly to Scotland and bike down. Always a juggle of work and like you, to do things as a couple. Convinced wife to bike just us in France along eurovelo 6 route 2018, was fun. So want to do a similar one in France again with her maybe next summer.
so many trip ideas, not easy to become reality always...
With regards to roads, steer clear of major A roads (so A9 in the Highlands), and you should be okay. You get used to the narrow roads, it was quite a shock when I moved out from the US. Car drivers aren't as aggressive as in the states, but they aren't great. Country lanes are great though.