I've taken coach trips all over the world, as a Tour Manager, for over 30 years so hopefully I can help a bit with your quandry.
I've also taken many people on coach trips around Scotland. Not wanting to drive is a really common reason for not wanting to take a coach holiday so you will find plenty of people in a similar position to you.
There are many different types of coach holidays. Some of them are definitely for older folks who enjoy more panoramic touring rather than being active.
However, there are plenty of options where you can be more active, either by enjoying activities that suit you in free time or because it's a more active group on the tour.
Glenton, Lochs and Glens, Newmarket, Great Railway Journeys, Grand UK holidays will give you some ideas of the difference. Great Railway Journeys combines coach and train travel to make an interesting tour experience.
Helpfully many coach holiday companies now give more information on the activity level, either in terms of walking distances covered or in terms of pace.