Oh that's a hard one!!! I like KindRedSpirit's suggestion to trust your gut.
One thing to think about is would you be okay with having your baby there if he/she decides to come? My sweet cousin traveled to our valley for our Grandma's funeral, she was 34 weeks, and felt fine. She ended up having her baby while here--and then had to stay longer than planned until baby could be d/c from the NICU and then had to travel home with a brand new little one. Not saying that this will happen (at ALL!!, I have never had a baby before 40 weeks) but if you would be okay with it, or not be okay with it, that is maybe something to factor in your decision. My cousin said (years later) it was kind of nice for her family to be around for the baby's birth (they mostly live here), so it worked out okay, and that she would do it again if she had to choose.
Personally, I wouldn't feel like traveling at 38 weeks. So even if I wanted to go, and was safe to go, and baby waited, it wouldn't be any fun for me. I have traveled for a wedding at 7 months before, and that was worth it to me. I hope you can find peace with your decision---such a tough one!!