Plot ideas for a journey? Why are they going? And where?

You have your story, and I think it's a good one. My first thought, a woman who cleans out the family bank account and leaves house, husband and children to join her "soul mate" that she met on the Internet. I think it would be more effective from the female point of view, as she would be expecting love and support and security at the end, and because husbands are less likely to forgive wives who take off than wives are to forgive husbands for such idiotic escapades.

This would be total fiction for me, but I think I could capture the gnawing fears, regrets and concerns of such a foolish and reckless last-ditch dive for fairy-tale romance.

If written from the masculine point of view, thoughts on the journey would be less important than the aftermath of reaching the disappointment of the destination.

I think that you should stick with your initial idea. If that came from you, that will be the one you write the best.

You could have the mum being reminded of all the things she missed out. She could see young children, an amusement park or playground, even a hospital which could make her think about the fear that every parent has about their children hurt or sick.