Welcome, momtohanna! I don't have gravel roads to contend with since I live in town, but I ride a mountain bike a lot of the time because the bigger, thicker tires aren't as sensitive to surface as the road bike tires. Personally, I just like the mountain bike - it handles better, I like the position, etc. But we have a bike rack and can carry the road bikes to a starting point if we want.

I haven't done BAK but from what I've heard, I wouldn't go with a heavier bike like a mountain bike for that. If you're planning on doing some longer rides, tours, etc., you might want to check into a touring bike and car transport options. There are lots of older threads you can search, or feel free to ask again as you're thinking it through!

Deb