Boyfriend's Mom's wedding and Covid

My SO of almost 2 years is going to his Mom's wedding in California (we are in the Midwest) on a yacht with his family. There will be 10-12 people there and unfortunately most of them are anti-maskers/Covid is a hoax people. We currently live with my parents (in their 50's and 60's) and my 2 adult brothers. Only one of my brothers is vaccinated and neither me nor my SO are. My sister offered for us to stay with her for the week we are out there so we don't have to stay on the yacht with 10 other people. He said he would rather stay on the boat. I am beyond frustrated and hurt by his choices and I can't figure out if this is just a rough patch or if this is the end.