My parents (59M and 56F) want me (21M) to drive 6 hours last minute across state borders on my birthday for a favour. How do I say no?

My mom and dad went on a camping trip around a week ago with some relatives. Essentially, as they were leaving today my father accidentally hit a tree with their trailer as they were backing out of the campsite. My mom told me he was going too fast, was already angry, and blamed everyone else. So now they need to get the trailer fixed in a nearby town (12 hours away from me). Although there is NO damage to the truck what so ever.

So I get a call from my mom today (who is in tears) explaining the situation. She said that my dad came up with this plan for me to a family friends’ house halfway between us and meet them up there. The drive would be 6 hours there and back tomorrow on my birthday. I didn’t understand why this would make sense, but my mom explained that he is trying to save the miles on his truck as they are planning to exchange it within a couple months. The truck is fully drivable but would have to go back down anyways to pick up the trailer in a couple weeks once it is fixed. She said I could use their other car and I’m sure they would help with gas money.

My dad hasn’t officially come to me about this yet. Is it ok that I feel angry and nervous about this? I have immense driving anxiety and fear that it will definitely ruin my birthday. The drive is not an easy one. I also was already sad that they planned this trip completely forgetting about my birthday and left me alone for the week. Sometimes I feel like my relationship with them is purely transactional. I don’t know how to set the boundary to say no for a few reasons.

For context, I have been living under their roof post college and rent free while I desperately look for a job. I am very grateful for this, but feel like I lose the ability to say no and have any say in my life in general. I feel like have been doing a lot for them when it wasn’t always convenient due to this power imbalance. I helped them renovate a house over the course of three weeks, I helped them rebuild our fence, and had to run a garage sale all weekend when they had something come up. This just feels like the last straw. Can I say no? How can I prevent this in the future? Thanks everyone.

TLDR: I don’t know how to say no to parents favours even when they are extremely inconsiderate. Seeking advice or wisdom.