Flying to Europe from CA 1st trimester

Hey mamas! I know this is crazy, but I’m about to fly from California to Europe on a 12 hour flight for a family vacation that I’ve had planned for almost a year. It’s for my grandpa‘s 90th birthday so I can’t cancel it. Any tips on being in my first trimester and being on a plane that long with a four-year-old sitting next to me😭