I found that - with the exception of getting wet (water parks, splash mountain) that 3 applications per day worked out for us. First in the morning, lunch time and late afternoon.
I would say the two of us used about 1/3 a regular sized bottle in 3 days. We did not get one spot of sun on us.
Don't forget your the part in your hair unless you are wearing a hat all the time. Spray works well for this - we wore hats, tho.