I'm going out for several hours this week with my newborn and wondered what I do for making up her bottle when out. She won't be feeding til at least three hours after we leave. Please advise what I do? Take empty bottles and ask for boiling water to mix with formula from pot? If so, is the empty bottle still sterile after several hours? I can't use ready maxes as my baby has lactose free? Do I need to buy a bottle warmer? Don't know anything about them!