I just had to throw out my 2 cents on this....Flip flops in parks scare me. Tennis shoes have a LOT more protection and support. Besides the sunburn and blisters, I would be afraid of her little toes getting squished. If your standing in line and a person steps back and on her foot. She's walking and trips, stubs her toe...ouch! Your getting on Small World and her flip flop does a flop in the water. Your walking through the park and stop to look at something just briefly, she decides to get out of the stroller and you start to move and catch her toes under the wheels. Another Ouch. There are just so many ways we can hurt our feet. Granted, these are worse case senarios, but still. I wouldn't want to "ruin" our trip when it could be prevented. Why not let her wear her Flip flops to the pool and on the cruise, or maybe out to dinner, but keep the tennis shoes for in the parks. I don't even like to let our boys wear their closed toed sandles to the parks. Tennies are just better....IMHO. Have a great trip!!