I'm so sorry that you're both suffering from IBS.
To answer your question, I often get symptoms when I've been sitting for too long, mostly bloating and discomfort. A longer car ride can definitely trigger that for me. Here's an article about sitting and constipation, in case you're interested:
https://irritablebowelsyndrome.net/living/sitting
In addition, any kind of traveling (including car rides) tends to stress me out, which can also cause my IBS-D to flare.
I hope that other people will soon share their experiences with you as well!
-Karina (team member)