Road Trip Tips

My boyfriend and I plan to get engaged before I go back to work June 10th. Where my boyfriend wants to propose is 3 hours away (without baby) and we typically do a potty break about half way. I need advice on how to make this trip possible with my baby who will be less than 6 weeks. We are driving and then his family will be watching the baby during whatever he has planned to actually propose. I would ask my mom but she didn’t do trips with us this young.