Third trimester road trip

My husband is determined to take a "baby moon" when I'll be 31 weeks. I didn't think it would be a big deal back when I agreed but now that I'm 29 weeks I'm starting to freak out reading about pre-term labor at high altitudes and all the other complications that can happen. My midwife doesn't see a problem with it as long as I get out and walk every two hours and wear compression socks. We are driving from MN to OR so it's a 24 hour trip one way. Anyone have tips or experience with this? Maybe I'm just panicking for no reason?