It's not just the sunscreen, you need sun hats and decent swimware. Will you be spending your entire vacation on the beach? Then I would purchase the swimsuits and coverups with SPF and get the sunhats that cover the back of the neck and their ears. For intense sun, I'd also purchase Baby sunglasses.
onestepahead.com had a great selection on sun products. A lot of the products are manuf. in Australia.
I would also purchase a stroller fan and a stroller sun canopy is a must! I have the Pepany, which I really love.
I'm a
travel agent and can't tell you how many times I've seen babies without proper sun protection. We were on a cruise docked in Key West and this 6 month old baby was in a cheapy $10 stroller with no canopy! She had nothing to shield her from the intense hot sun. No sun hat either!!! My kid had his sun stroller canopy and sun fan and was fast asleep in comfort.
Sunscreen is just not enough protection.
PS I use Coppertone Waterbabies and just bought the Tinkerbell Spray can of Baby sunblock from disney shopping online. I think the spray cans are easier with little kids. I also stock up on the 99 cent small travel size baby sunblock anytime I see them in
Walmart. I keep one in each handbag, baby bag, stroller, etc.... I have them everywhere.