Just go for it. I've done the trip to Australasia several times with my children at varying ages and actually 6 months is a good age. Go with Singapore or Virgin. If you can possibly afford it, go premium economy for a bit of extra space. Don't worry about 'germs' They won't pick up anything they won't get at home. Food wise, take some jars of puree. The crew are very good at heating bottles if you are not still BF. Its a tiring trip but but easier when they're at the age of not wriggling to get down or crawling over the seats. Also at six months you'll still be able to use the sky cots. Have a great time!